Studies in Macrosiphonia ( Apocynaceae ) : Generic Recognition of Telosiphonia

ABSTRACf Woodson recognized two subgenera within Macrosiphonia (Apocynaceae: Apocynoideae), a South American subgenus Eumacrosiphonia, and a North American subgenus Telosiphonia each with five species. Both taxa are characterized by low subshrub-shrub, nonviny growth habits, white, long-tubed, vespertine corollas of a type associated with moth pollination. Their distinctive anther and style-tip characteristics show each is related to a group of genera around Mandevilla and Mesechites. The two subgenera, however, differ strongly from each other in inflorescence, style-head structure, and pollen size indicating that they are not sister taxa and that Macrosiphonia as currently recognized is poly-phyletic. Thus the subgenus Telosiphonia is elevated to generic rank consisting of six species with one species and one variety described as new.


INTRODUCTION
Preparation of a treatment of Apocynaceae for the Chihuahuan Desert Flora and the discovery of a new species have resulted in this revision of North Americian Macrosiphonia Miill. Arg. The last revision of the genus was completed by Woodson (1933), who incorporated two distinct elements in the genus, the true Macrosiphonias (his subgenus Eumacrosiphonia) consisting of five South American taxa, and five North American taxa that he recognized in subgenus Telosiphonia Woodson. The genus is a member of the subfamily Apocynoideae (then called Echitoideae) and within the subfamily is related to the large tropical genus Mandevilla Lindl., with which it shares distinctive anther and stigma structures (Woodson 1933).
The taxa Mandevilla, Macrosiphonia (s.l.) Allomarkgrafia Woodson, Mesechites Mull. Arg., Tintinnabularia Woodson, and Quiotania Zarucchi, if one wishes to recognized this wealky differentiated genus, form a distinctive group within the Apocynoideae. They all have anthers that are indurated throughout the abaxial surface except at their membranous terminal appendages. Their anther sacs are confined to the distal one half to two thirds of the interior anther and the expanded anther base is a sterile, somewhat flattened structure that is obtuse to truncate and either notched or auriculate at the base (except in Mesechites where anthers are fertile to the base). The short filaments join the anthers near the base of the anther sacs and connect shortly below the anthers to the corolla tube, except in Tintinnabularia, which has long filaments. The style heads are located directly beneath the fertile portion of the anthers and are surrounded by the sterile anther bases and filaments. The five anthers together form a cap over the style head. The lower portion of the anther develops special hairs that are secretory and they become cemented to the style head by an adhesive material causing the style and anthers to form a gynostegium (Fallen 1986). In Mandevilla, this adhesive material is secreted by the filament hairs, while in other Apocynaceae the material is secreted by the style head (Fallen 1986). The adaxial filament surface often contains a dense beard of short to long, reflexed hairs that play a role in the formation of the gynostegium, called a retinacle by Pichon (1948).
The expanded style heads are rhomboid in shape but distinctly five ridged, at least at the base, with the ridges extending towards and contacting the medial portion of the filaments and fitting in the recess just below the fertile anther sacs. According to Fallen (1986) the style head is stigmatic in a zone below the five ridges. The clear adhesive material fills in the space between the five ridges and the upper filaments. By anthesis, the anther sacs are open, shedding pollen upon the style head. The pollen is prevented from reaching the stigmatic area at the base of the style head by the presence of the clear adhesive material that fills the area between the style head and the surrounding sterile part of the anthers and filaments. When a pollinator visits the flower, its proboscis is guided outside the androecium to holes between the filaments; upon withdrawal, the proboscis is drawn into the slits between the sclerified anther bases where downward pointing hairs scrape off the pollen in an area near the stigmas. The retreating probosis is pulled through the adhesive material and up through the fertile anther sac area picking up pollen on the attached adhesive material (Fallen 1986). The system found in the Apocynoideae is considered the most advanced in the family (Fallen 1986).
The seven taxa are also distinguished by the presence of distinctive foliar glands (colleters) located along the distal petiole and the basal adaxial midrib (Thomas and Dave 1991). In subgenus Exothostemon of Mandevilla they are also scattered along the adaxial midrib. The glands are fusiform, 0.2-0.4 mm long and quite conspicuous. In the North American Macrosiphonias and in some Mandevillas the glands also occur in the stipular region at the base of the petiole. Similar fusiform glands, known as "squamellae" (Woodson and Moore 1938) occur scattered inside the base of the sepals in all the above groups as well as other members of both subfamilies. Colleters, however, are not unique to this group within Apocynaceae (Thomas and Dave 1991). Woodson (1933Woodson ( , 1936 considered that the distinctive anther, stigma, and colleter features separate these taxa from the remainder of the subfamily. Leeuwenberg (1994) also places Macrosiphonia, Mandevilla, and Mesechites together in his tribe Echiteae, subtribe Echitinae, but he does not recognize Allomarkgrafia or Quiotania, and places Tintanabularia (sic) in a separate tribe Wrightieae, subtribe Wrightiinae.
Each of the above genera has some distinctive feature that distinguishes it from the others. Allomarkgrafia (six species : Gentry 1989) has highly branched, crowded inflorescences, divided racemes, distally constricted corolla tubes, filaments strongly decurrent on the inner corolla tube, nectaries larger than the ovary, and fusiform style tips (Woodson 1936:599). Tintinnabularia (one species) has dichasially branched or subumbellate inflorescences, domatia in the axils of the secondary veins and midveins on the abaxial leaf surface, reduced corolla tubes with much elongated corolla throats, anthers with slender tips and long slender filaments and short, distinctive style tips (Woodson 1936:610). Mesechites (ten species,) again has highly branched inflorescences, distally narrowed corolla tubes, and narrowly tapered style heads. The recently described Quiotania (one species) is very similar to Mandevilla differing apparently in its lacking a narrow, basal corolla tube and in having an attenuate style head (Zarucchi 1991).
Mandevilla (ca. 150 species) can be distinguished from the two subgenera of Macrosiphonia by a series of vegetative and floral features. Mandevilla species are woody or woody-based lianas, less frequently subshrubs or herbs, while the two groups within Macrosiphonia are shrubs, subshrubs to strongly rhizomatous subshrubs-none is viny. Interestingly the northernmost Mandevilla, M. karwinskii (Miill. Arg.) Hemsl. is a rhizomatous subshrub with a habit similar to that found in some northern Macrosiphonias, except that its upper stems still tend to twine. Flowers of Mandevilla are mostly salverform to funnelform with moderately short tubes and they may or may not have ex-panded throats. Inflorescences of Mandevilla are largely simple racemes, but may be reduced to single flowers. Inflorescences in North American Macrosiphonia, in contrast, are solitary or in monochasial-dichasial unbranched cymes; those of South American taxa appear to be derived from thyrses (Woodson 1935:31). Mandevilla flowers are diurnal, apparently pollinated by various diurnal-active insects. The distinctive white, long, salverform flowers of both subgenera of Macrosiphonia appear to be vespertine and appear strongly modified for moth pollination, (Endress 1994:319) most (not all) producing a strong perfume in the evenings. Although there are no published studies specifically verifying moth pollination in either subgenus of Macrosiphonia, Grant (1983) places both M. macrosiphon (Torr.) A. Heller and M. brachysiphon (Torr.) A. Gray on his predicted list of United States-Canada moth-pollinated species. Woodson (1933) distinguishes Macrosiphonia from Mandevilla on the basis of style-head structure noting that the style heads of Mandevilla are "pentagonalumbraculiform," i.e., the five prominent style ridges curve downward to a distance about equal to their point of divergence from the distal style conforming to a shape like a five-ribbed umbrella. In contrast style heads in both subgenera of Macrosiphonia are said to be "pentagonal-subglochidiate," i.e., the five stigmabearing ridges curve retrorsely well below their point of attachment to the distal style in a glochidate fashion. However, in my dissections of Mandevilla flowers, I have found some stigmas, e.g., Mandevilla sellowii (Miill. Arg.) Woodson and others, that approach the subglochidate condition found in Macrosiphonia where, in contrast, some flowers of M. brachysiphon produce style heads that are not glochidate. Thus I question the consistency of this characteristic.
Of the above characters, the nonviny, fruticose to suffrutescent growth habits, the long, white vespertine, presumably moth-pollinated flowers, and the glochidate stigmas were characteristics used by Woodson (1933) to maintain Macrosiphonia as a genus separate from Mandevilla. Woodson (1933Woodson ( , 1935 clearly questioned whether the two subgenera of Macrosiphonia were congeneric, noting that their ranges roughly coincide with the extreme northern and southern distributions of Mandevilla. He noted it would be more logical to consider that the distinctive flowers arose independently in the two subgenera rather than representing the remnants of a once continuous distribution. He further noted that the distinctions between Macrosiphonia and Mandevilla were very tenuous at best.

MATERIALS AND METHODS
This study is based primarily in empirical evidence derived from studies of specimens of Apocynaceae VOLUME 14, NUMBER 3 and from the literature. Material of North American Macrosiphonias was borrowed from or observed at A-GH, ARIZ, F, NY, RM, RSA-POM, TEX-LL, US.

RESULTS AND DISCUSSION
As noted above, the two subgenera, Macrosiphonia and Telosiphonia, both occur in arid zones outside the distribution of the largely tropical Mandevilla. Each appears to have modified the basic flower type towards moth pollination-both are characterized by longtubed, white, salverform, vespertine flowers of a type visited by moths. Both are nonviny shrubs-subshrubs, with thickish, subcoriaceous leaves that are strongly vestitured beneath, green above.
The two subgenera, however, have distinct differences in inflorescence structure, style-head structure, and pollen size that give evidence that the two subgenera are not sister taxa. Species in both subgenera produce terminal flowers or inflorescences from actively growing shoots of the year (Fig. 1, 3A). The shoots cease vegetative growth, produce lateral shoots from the axillary buds of the terminal pair of leaves and these shoots often overtop the flowers. Members of subgenus Telosiphonia typically produce either one or two, rarely three, flowers in a reduced inflorescence derived from a determinate simple dichasia, with two bracts separating the peduncle from the longer or equal-lengthed pedicel-the small bracts do not directly subtend the calyces ( Fig. 4B-C). When more than one flower is produced, the lateral flower(s) develop in the axils of the bracts on lateral pedicels (not peduncles) ( Fig. 2A). Inflorescences are simple and the pedicel usually is much longer than the peduncles except in one species, Macrosiphonia. hypoleuca (Benth.) Miill. Arg., which may have moderately long, rarely quite long, peduncles ( Fig. 2A).
In the South American subgenus Macrosiphonia the taxa also produce terminal flowers bordered by axillary shoots. But the peduncles are greatly elongated, 10-45 em long, while the pedicels are typically absent with the bracts directly subtending the calyces (Fig.  lA). This condition strongly differs from that found in subgenus Telosiphonia. When more than one flower is produced, the inflorescence branches at the bracts immediately below the flower, and the lateral axis consists of an elongated peduncle (not pedicel), which overtops the older flower, producing bracts directly under the next flower ( Fig. lA). If additional flowers are produced, they again are produced at the base of the previous flower and extend on an elongated peduncle. Woodson ( 1935) considers this to be a modification of a thyrse, not a simple dichasium as in the North American species.
The style heads of the two groups differ strongly. In the North American subgenus Telosiphonia the 181 style heads have five narrow ridges that extend and expand from the tip, each directly opposite a filament. The ridges are of uniform width and lack any basal skirt or collar (Fig. 2I, 4I). In the South American subgenus Macrosiphonia the style heads are larger and the five style ridges are narrow and marginally concave but expanded below, each having a distinct, thin, lower-margin skirt or collar that extends along the base of the projected ridge that indents around the adjacent filament (Fig. lC). The style heads of the subgenus Macrosiphonia are also associated with abundant translucent adhesive material, while this is much less abundant, possibly absent, in subgenus Telosiphonia.
A routine survey of water-mounted pollen revealed that, while the pollen of both subgenera is triporate, as are most the Apocynoideae (Nilsson 1990), the pollen of the subgenus Telosiphonia is large (Erdtman 1966), ranging from 53 to 78 j.Lm in diameter, but that of subgenus Macrosiphonia, is very large-the grains of M. longiflora (Desf.) Miill. Arg. measured 180 j.Lm (0.18 mm) in diameter! This large pollen, however, may correlate with the large corolla size of that species.
There are also differences in the size of the hairs that extend into the throat from the inner surface of the free filaments. In the North American taxa they are short, about 0.3 mm in length (Fig. 4H), in the South American taxa they are much longer, to 1.5 mm long (see Fig. 41g in Meyer and Burkart 1979).
The data presented above indicate that substantial differences exist between the two subgenera of Macrosiphonia, as recognized by Woodson. It forces us to consider whether the two subgenera are sister taxa or are polyphyletic with the taxa being drawn together by their conspicuous large corollas associated with a convergent pollination system. The latter was suggested by Woodson (1935) who, incidentally, also annotated many North American herbarium sheets as belonging to his proposed genus Telosiphonia, which he later relegated to subgeneric rank.
The morphological differences noted above, particularly those of inflorescence and style structure, in my opinion, strongly support that Macrosiphonia is polyphyletic. While the amphitropical distribution can serve to delimit the two taxa, it in itself is not significant, as Raven (1963) notes many examples of genera and species with similar broad distributions. The distinctions between these two taxa, rather, is morphologically based. As both taxa occur in semiarid habitats, it may well be that some of their vegetative similarities, e.g., their subshrub-shrub growth habits, strong vestiture, may represent character convergence.
As to how to best treat the taxa nomenclaturely, there appear to be three options: (1) If both subgenera have been derived independently from Mandevilla, they are then both paraphyletic in relation to Man-  devilla and one could support combining both subgenera within the older Mandevilla. (2) If the two subgenera are both derived from some other common ancestor basal to Mandevilla, they could be combined with this taxon. (3) If the two subgenera have been derived independently of one another, from diverse ancestors, then one could and should combine them with their respective groups or recognize both as distinct genera.
Unfortunately the data obtained from gross morphology do not give evidence of the exact phylogenetic origins of the subgenera of Macrosiphonia. The placement of both subgenera within Mandevilla, the first alternative, would place the strongly different inflorescence type of the South American Macrosiphonias in with the largely racemose Mandevilla. This would breakup the continuity of Mandevilla, and weaken its distinction from Allomarkgrafia and Mesechites, promoting recognition of a single highly variable genus based on the occurrence of foliar glands and a distinctive obtuse-truncated anther base. The distinctive inflorescence type of the South American Macrosiphonias would still be a discordent character within the expanded genus, and the genus would not correspond to the rather finely drawn genera occurring in the remainder of the Apocynoideae (Woodson 1933, 1935, Pichon 1950, Leeuwenberg 1994).
As noted above, the other recognized genera related to Mandevilla all differ in morphological characteristics that separate them from one another and from the subgenera of Macrosiphonia. Rather than combining the subgenera of Macrosiphonia into these distinctive genera and disrupting their continuity I have elected to recognize the North American taxa as a distinct genus by raising Woodson's subgenus Telosiphonia to the rank of genus. This allows recognition of the polyphyletic basis of the current Macrosiphonia while causing minimal nomenclatural disruption.
Before presenting the formal classification of the species of Teliosiphonia I wish to comment on strong variation found in the constituent species. The plants apparently strongly respond to variation in available water resources. In wet years plants show luxurient growth with large leaves and long internodes, but in dry years, plant growth is reduced and leaves, internodes and flowers are smaller. One finds strong variation in overall flower size with plants with large leaves producing large corollas, while other specimens with smaller leaves have much smaller corollas. Strong variation also occurs in flowers of single collections; overall variation of corolla size is widespread in the Apocynaceae (Bruce Hansen, pers. comm. 1995). The result is considerable variation in corolla sizes within a species, e.g., corollas range in total length in T. hypoleuca from 3 to 8.5 em, in T. brachysiphon from 3.6 to 7.2 em, in T. macrosiphon-ALISO ia from 8.5 to 15 em, etc. In most species the smallest corollas are half the size of the largest ones and in several taxa these extremes have been recognized nomenclaturely. CLASSIFICATION Telosiphonia (Woodson) Henr., comb. nov. Shrubs, subshrubs, sometimes strongly rhizomatous, with white latex, branched or unbranched above. Leaves mostly opposite, short-petiolate to sessile; leaf blades rather coriaceous, entire, often undulate-margined, often bicolored, densely white tomentose beneath, less strongly vestitured above or equally vestitured on both surfaces, the stipular area, adaxial petiole and adaxial basal midrib with clusters of small fusiform glands (colleters). Flowers developing from the tip of active shoots of the season, often overtopped by lateral stems formed from the axils of the uppermost leaves; peduncles reduced to moderately long; bracts 2, small, leafy; pedicels usually longer than peduncles; the flowers solitary or if more, 1(-2), developing from axils of bracts forming a simple monochasium or dichasium; sepals 5( -6), linear-lanceolate, separate, entire, herbaceous or petaloid and drying reddish, with a single series of distinctive fusiform squamellae produced at the adaxial sepal base; corollas salverform, whitish, often marked with red in bud, vespertine, usually sweetly aromatic in the evening, the tubes slender, long, abruptly expanded to broader cylindrical throats, the lobes 5, asymmetrical, dextrorsely convolute, spreading; stamens 5, included in the basal throat, anthers indurate except at the membranous acute tip, connivent, fertile in the distal half with 2 parallel anther sacs, sterile in the lower half with the the base truncated, notched, often auriculate; the filaments short, attached medially at the top of the sterile portion, adnate to the corolla just below the anther base, the filament bearded inside with retrorse hairs; pollen spheroidal, triporate, yellowish. Ovaries 2, surrounded with a sheathlike nectary consisting of 5 basally united, rectangular lobes; styles united just above ovary; style tip capitate, 5 ribbed, located at the base of fertile portion of anthers, with the ribs extending to the filaments, the ribs retrorsely extending making the style tip glochidate in shape, the lobes stigmatic near their base. Fruit of paired, terete to slightly tortuous, brownish elongate follicles; seeds elongate, attached marginally to the placentae; coma dense, distal, of straight, white to tawny hairs. With seven taxa in North America distinguished in the key below.

Macrosiphonia
A. Corolla tubes 0.4-1.5 times as long as the expanded corolla throats; corollas 4-7 em long, the slender tubes 1-2.5 em long. B. Leaves bicolored, green above, white-tomentose beneath, oblong, oblong-linear, oblong-lanceolate, oblong-ovate, 2-6(-9) em long, 0. Rhizomatous suffrutescent perennials 1.5-7.5 dm tall; stems of season developing directly from the thick rhizomes or from the base of older stems of the previous years growth, rarely from larger subterranean roots, erect, strict or variably branched, woody; internodes (7-)20-35(-94) mm long, dark red-maroon, densely covered with persistent short crinkled hairs 0.1-0.3 mm long and with larger, curved, eventually deciduous hairs to 0.4 mm long. Leaves 2(-3) per node, opposite to subopposite; leaf blades linear, oblong, oblong-elliptical to oblong-ovate, (2.2-)3.5-5 (-7.3) em long, (4-)8-17(-21) mm wide, acute, sometimes rounded, always apiculate at the apex, rounded to usually slightly cordate at the base, entire, sometimes revolute, rarely undulate along the margins, strongly bicolored, the upper surface green, closely speckled with red, closely pubescent to hirtellous with curved or erect hairs 0.1-0.2 mm long, often rather rugose with veins impressed, the lower surface white, densely canescent-tomentose with matted crinkled arachnoid hairs to 1.0 mm long, the veins, except the midrib, obscure, yellow or reddish. Flowers 1-2(-3) at the tips of new-growth stems, usually overtopped by lateral branches; peduncles (0.5-)10-22(-36) mm long; bracts 4-7 mm long, linear; pedicels 7-15 mm long, the peduncle-pedicles vestitured as on the young stems; sepals 5, oblong-linear, 7.2-10(-12) mm long, 1.2-2 mm wide, attenuate, reddish, membranous; corollas white, externally tinged or striped with red or pink, (36-)50-70(-85) mm long, the tube (8-)15-30 (-45) mm long, the throat (13-)17-25(-30) mm long, 7-9 mm wide, the lobes 15-29 mm long, 14-28 mm wide, the open corolla 38-65 mm in diameter; anthers 9-11.5 mm long, 1.5-2 mm wide. Paired fruit (8-) 11.5-15 mm long, 3-5 mm wide, reddish brown, closely pubescent with tightly coiled hairs; seeds rustybrown, 9-10 mm long; seed coma, whitish, turning tawny, 14-21 mm long. Telosiphonia hypoleuca is characterized by its strongly bicolored, mostly oblong to oblong-ovate leaves, by its corollas with tubes shorter than to as long as the throats, by its narrow, thin sepals that dry a rusty-red color, and by a tendency to have an erect, single-stemmed growth habit. The species shows strong variation in corolla size, ranging from 3.6 to 8.5 em in overall length. Inflorescences may have 1-2 or 3 flowers, with peduncles typically 10-22(-36) mm in length (the longest in the genus) and pedicels 7-15 mm in length. Growth habit also varies, ranging from plants with series of strict, erect stems developing from rhizomes to highly branched subshrubs-shrubs with new growth developing from nodes of the previousyears branches. The species is easily recognized by its bicolored, oblong leaves that range from linear to oblong-ovate. Occasional specimens have very narrow leaves and one such specimen was the basis of Macrosiphonia wrightii, but the specimen agrees with the species in all other floral and vegetative characteristics. The high degree of variation in plant and flower size is considered to reflect the season's environmental conditions as there is no correlation with flower and plant size with geography except that most plants have short corolla tubes to 2.5 mm long.
The species ranges widely from the mountains of trans-Pecos Texas to Chihuahua, Sonora, and Tamaulipas south to the state of Mexico where it occurs in rocky pine-oak forests and woodlands, and grassland ecotones, mostly in igneous-derived soils from 450 m (Barrancas in Sonora) to mostly 1000-2600 m elevation (Fig. 5). Flowering occurs from June to August (September) following rains. The common name for this and most species of the genus is Flor de San Juan. 2. Telosiphonia brachysiphon (Torr.) Henr., comb.
The species is characterized by its largely suffrutescent growth habit with new stems developing from the base of the previous year's plant, by the concolorous leaves with a close vestiture of mostly tightly curled hairs, the corollas with short basal tubes, and small calyces that dry a maroon-red collar.
Disjunct collections from the vicinity of Alamos, Sonora and adjacent Chihuahua differ in having larger corollas, a more shrubby growth habit, and rather narrow undulate-margined leaves. Collections from these populations have been described by Woodson as Macrosiphonia brachysiphon var. magnifica and by Standley as M. woodsoniana. The Gentry collection described by Standley also has slightly denser leaf and stem vestiture and a widely branched shrub habit. Most all of the characteristics found in these and other collections from the region fit well within the variation ofT. brachysiphon and thus the taxa are not recognized here. While the corollas of the plants are large, they do not exceed the size found in scattered collections throughout the range of T. brachysiphon. It is not known if the tendency of these plants to have a shrubby growth habit is a factor of their occurrence in a nondesert habitat or if it is the product of past introgression with T. lanuginosa, which also has larger corollas and undulate-margined leaves. However, the corollas of T. lanuginosa are much larger, and have much longer tubes than those found in the above noted collections.
On the eastern margin of its range the species appears to blend into T. lanuginosa as they both form small plants with coarse, densely vestitured leaves.
The possible introgression and distinction of these taxa is discussed under T. lanuginosa. Telosiphonia brachysiphon also has a subshrub habit, but this taxon is easily distinguished by its thin, green leaves, short corolla tubes and its Arizonian-Sonoran distribution. As with other species of the genus, the taxon is highly variable in flower size, leaf size and texture with sizes reflecting environmental conditions.
Telosiphonia lanuginosa, the first North American species described, is characterized by its small membranous, reddish sepals with a vestiture of moderately long hairs, by its very short to absent peduncles, short pedicels, its long corollas usually with greatly elongated tubes.
The southernmost populations of T. lanuginosa in Puebla and Oaxaca are distinguished by having shorter corolla tubes and other characteristics that suggest introgression with T. hypoleuca. These latter plants are herein recognized as a variety of T. lanuginosa and thus the species consists of the following two taxa: Plants divariactely branched shrubs with the new years growth developing from the older upper stems. Leaves highly variable in shape, size and thickness but tending to be oblong-ovate, oblong-obovate, oblongoblanceolate, narrowly elliptical to ovate, 15-30(-40) mm long, 7-16(-25) mm wide, acute to rounded-truncate, apiculate at the tip, often with strongly undulate, closely revolute margins. Flowers with corolla throats 14-22 mm long, the corolla tubes 50-80(-105) mm long, (2.6-)3-5( -6.5) times as long as the corolla throats.
The type variety can be distinguished on the basis its small shrub habit, often small, strongly undulatemargined leaves, thin, often reddish sepals and long corolla tubes. The taxon is highly variable in many of these features particularly in leaves with some specimens exhibiting thick, strongly undulate margined leaves and others having thin, entire leaves. Leaves of the plants from Hidalgo are often larger, more ovateorbicular than those found in other areas.
The taxon is often difficult to distinguish from T. macrosiphon as they are very similar in leaf characteristics and flower structure. They usually can be distinguished on the basis of growth habit with T. macrosiphon having a more suffrutescent habit with new shoots of the season developing from a root crown or from lower branches of the previous year (sometimes from rhizomes), while var. lanuginosa has a divaricately branched small-shrub habit with new branches of the year developing further up the stems. It is considered that the desert-dwelling T. macrosiphon may die back completely during the dry season, regrowing each year from basal shoots, while T. lanuginosa, that occurs in scrub and grasslands mostly east of the deserts, is more of a true shrub either with perennial leaves or developing new shoots from its upper stems. The narrower, strongly undulate-margined leaves also serve to distinguish most specimens of var. lanuginosa, however undulate margins also occur in T. macrosiphon. A secondary feature for distinguishing the two taxa lies in the calyx. Calyx lobes of var. lanuginosa are typically shorter at anthesis and in dried specimens, are thinner, of a more uniform rusty-red color, which closely matches the color of the dried corolla tube. Calyx lobes of T. macrosiphon, in contrast, are larger, thicker and tend to be green-herbaceous, although most are reddish along the thickened, medial base and streaked with red towards the lower margins. Sepal length, however, tends to mirror vegetative size. Plants of var. lanuginosa showing strong vegetative growth have sepals 13-14 mm, approaching ALISO those of T. macrosiphon in both size and texture (Runyon 2738, Hidalgo Co., TEX.). Likewise, some plants of T. macrosiphon that appear drought stressed with small leaves also have shorter calyx lobes, and sometimes shorter corollas (LeSueur 174, Chihuahua, TEX).
In its short peduncles-pedicels, membanous sepals, and divaricate shrub habitat T. lanuginosa also is similar to T. nacapulensis and T. hesperia. Telosiphonia nacapulensis, however, can be distinguished by its larger shrub habit, reduced leaf vestiture, smaller corolla lobes, and its ususually close sepal vestiture; while T. hesperia can be distinguished by its dense leaf vestiture and by its tendency to have more orbicular, broadly ovate leaves and herbaceous sepals. However, as noted previously, populations of var. lanuginosa from Hidalgo may also have broadly ovate-orbicular leaves. The subshrubby, short corolla-tubed, green-leaved T. brachysiphon is easily distinguishable from this taxon as is the oblong-leaved T. hypoleuca. However, the southernmost populations of T. lanuginosa, described as a new variety below, have characteristics intermediate between the var. lanuginosa and T. hypoleuca. Woodson (1933) considered T. lanuginosa to be intermediate in morphology and distribution between T. hypoleuca and T. macrosiphon and suggested a hybrid origin of T. languinosa. In its narrower leaves, that are less strongly vestitured on the upper surface, and the much smaller, reddish calyx lobes, T. lanuginosa does indeed approach T. hypoleuca. It does not, however, exhibit the longer peduncles and shorter corolla tubes characteristic of T. hypoleuca.
The new variety can be distinguished from var. lanuginosa solely by its shorter corolla tubes. In addition most specimens are low, weak-stemmed subshrubs with trailing stems and some specimens have rhizomes. The leaves are slightly larger than in the type variety, are more oblong-ovate to oblong-elliptic, bicolored, and moderately thin. They taper to an acute tip and are closely rounded to slightly cordate at the base. In their oblong shape the leaves are somewhat reminescent of those of T. hypoleuca and most specimens of this taxon have been identified as T. hypoleuca by collectors.
In corolla tube length the taxon is intermediate between T. hypoleuca and var. lanuginosa with var. oaxacensis having corolla tubes 33-45 mm long, 1.6-3.2 times as long as the corolla throats, while those of T. hypoleuca are 8-30 mm long, only 0.4-1.5 times as long as the adjacent corolla throats, and those of var. lanuginosa are 50-80(-105) mm long, (2.6-)3-5 (-6.5) times as long as the corolla throats.
In all characteristics var. oaxacensis appears intermediate between T. hypoleuca and var. lanuginosa leading one to suggest that these disjunct populations, south of the Sierra Madre del Sur, may have both taxa in their origin. The collections available are quite uniform vegetatively and have leaves very similar to a collection of var. lanuginosa from San Luis Potosf (Purpus 5206), which caused me to consider oaxacensis a variety of T. lanuginosa rather than a variety of T. hypoleuca. It, of course, could be considered a distinct species, but I consider it adequately treated as a variety of T. lanuginosa. 191 All specimens observed of var. oaxacensis have flowers solitary at the stem tips with moderately short pedicels and no or highly reduced peduncles as in var. lanuginosa. In contrast, var. T. hypoleuca typically has well developed peduncles, mostly 10-22, rarely to 36 mm long, and occasional specimens have 2, rarely 3, flowers at the stem tips. But occasional specimens of T. hypoleuca  Much to weakly branched, deciduous, spreading shrubs (5-)10-20 dm tall, often wider than tall; young stems yellowish green, soon turning reddish maroon; internodes (5-)20-45(-57) mm long, initially densely villous with short, tightly curled hairs to 0.1 mm long and with longer straighter-curved hairs to 0.3 mm long, tardily glabrescent. Leaves opposite; leaf-blades broadly ovate, orbicular, sometimes reniform, 15-30(-56) mm long, 11-30(-56) mm wide, mostly shorter than the subtended internodes, rounded to acuminate, always apiculate at the tip, rounded to cordate at the base, entire to very slightly, coarsely undulate at the margins, bicolored, the upper surfaces green to olive-green, moderately to densely velutinous with erect hairs 0.3-0.5 mm long, the lower surfaces densely white tomentose with dense, curled hairs 0.3-0.8 mm long with the midvein and secondary veins yellowish; petioles 2-6 mm long, yellowish, densely tomentose with curled hairs. Flowers terminal, solitary at tips of new-growth stems, overtopped by 1-2 lateral branches; peduncles 0.2-1 mm long; bracts sepallike, lanceolate, acute, 6-9 mm long; pedicels 2-5(-9) mm long, thick, yellowish, tomentose; sepals 5(-6), oblong-lanceolate, (7-)9-12.5 mm long, 2-3.5 mm wide, acute, green, sometimes herbaceous distally when young, more yellowish below, villous-tomentose with curled hairs to 1 mm long outside and near medial tip inside; corollas white or lavender externally in bud, opening mornings to late afternoon (Carter & Moran 5495), 6.5-11.5 em long, the tubes 42-63 mm long, the throats 11-12 mm long, tubular to conical, the lobes strongly oblique, 18-24 mm long, 13-18 mm wide; anthers 8.5-9 mm long; filaments ca 1.5 mm long. Paired fruit (5.2-)10-19.5 em long, 3-4 mm wide, closely vestitured with tightly coiled hairs; seeds 8-10 mm long, rusty brown; seed coma 15-18 mm long, whitish.
The species is characterized by its large-shrub growth habit, its long flowers with tubes much exceeding the length of the throat, by the orbicular to broadly ovate leaves, by tendency for the young sepals to have green herbaceous tips that eventually fade and become membranous after anthesis, and its distribution in southern Baja California, Mexico. The leaves are distinctly bicolored, green and densely velutinous with erect, straight hairs on the upper surface, white, densely canescent with curled hairs and the veins are white, not reddish beneath. Insufficient specimens are avail- able to determine the typical flowering period, but the species appears to be drought deciduous, producing leaves and flowers in the late summer-fall with flowers appearing on the new growth of the season typically from September to October.
The species is known from rocky igneous slopes along the eastern edge of southern Baja California del Sur from south of Santa Rosalia to well south of Lo-reto and on several islands in the Gulf of California (Islas San Marcos, del Carmen, Catalina, Santa Cruz, Espiritu Santo, Ceralbo (Johnston 1924) from 50 to 1200 m elevation (Fig. 5). Common associates include species of Lysiloma, Prosopis, Erythea, Bursera, Jatropha, Fouquieria, Karwinskia, Sapium, Pachycereus, etc. A common name given with Carter specimens is "Jasmin de la Sierra." 6. Telosiphonia nacapulensis Felger & Henr., sp.
The species is characterized by its deciduous, divaricately branched shrub habit, by the ovate leaves that tend to have distinct, rather long acuminate tips and either entire or undulate, sometimes revolute margins, by the moderately short, mostly thin sepals with a characteristic short vestiture, and by the very long corolla tubes and relatively short corolla lobes. The specimens vary greatly vegetatively. Some plants show evidence of vigorous growth with long internodes, large, fiat, green, rather sparsely vestitured leaves, other specimens have reduced new growth with crowded nodes, crooked stems, thick, often revolute or cupped, hairy leaves. Lower leaf vestiture also varies, even on fast-growing plants, with some plants having white, canescent-tomentose lower surfaces with other plants having a much less dense vestiture.
The new species appears closely related to T. brachysiphon having similar sepals and leaves, but it differs in its larger, woody shrub habit, much longer corolla tubes, and often somewhat thicker leaves with dense abaxial vestiture. Of note the southermost collections ofT. brachysiphon also tend to be more shrubby, as in the type of Macrosiphon woodsoniana, but these plants lack the greatly elongated corolla tubes characteristic of T. nacapulensis. In its shrubby habit, leaf shape and vestiture, and sepals the new species also resembles T. lanuginosa, however the corolla diameter of T. nacapulensis (measured lobe tip to tip in pressed flowers) ranges from 3 to 4 em, while the flowers of T. lanuginosa are much larger, typically 5-8 em in total limb diameter.
The new species is known from the dry reddish and yellowish rhyolitic Sierra El Agua (part of the larger Sierra el Aguaje), north of Bahia San Carlos, and the Sierra Libre, between Hermosillo and Guaymas (Fig.  5), where it occurs in scattered populations on steep, dry, rocky canyon sides with Acacia willardiana, Bursera microphylla, Haematoxylon brasiletto, Jatropha cuneata, Macroptilium atropurpureum and various cacti. The species is cultivated in Tucson. Flowering occurs in following rains in August-October with flowers terminating new growth of the season. The flowers opening in the late afternoon and fail during the following morning.