Aliso: a Journal of Systematic and Evolutionary Botany Wood Anatomy and Familial Status of Viviania Wood Anatomy and Familial Status of Vivian/a

Wood of three species of Viviania from Chile was studied. The wood has growth rings, moderately grouped vessels, helical sculpture in vessels, fiber-tracheids with small pits, and various degrees of storying. Axial parenchyma and rays are absent, regardless of age of stem. These facts are in accord with close relationship to other genera of Geraniaceae s.l. Viviania differs from other Geraniaceae in presence of borders on imperforate tracheary elements and presence of endosperm; other differences (polyporate pollen; loculicidal capsules) are shared with some other genera which have familial status according to some authors, subfamilial status according to others. Viviania is probably the most distinctive element within Geraniaceae s.l., but other genera are close behind in this regard. Wood features of Viviania are in accord with the dry habitats occupied by this genus.


INTRODUCTION
The genus Viviania consists of 28 species native mostly to Chile, but a few species occur in Uruguay and southern Brazil (Knuth 1912).Viviania constitutes either a subfamily of Geraniaceae or an independent family according to recent authors.Advocates offamilial status include Dahlgren (1980) and Thome (1983).Those who retain Viviania within Geraniaceae as a tribe or subfamily include Cronquist (1981), Hoffmann (1978), Knuth (1912), Munoz (1959), andTakhtajan (1980).The features by which Viviania differs from Geraniaceae other than Viviania include (data from Knuth 1912) polyporate nature of pollen (tricolpate in Geranieae, polyporate or nonaperturate in Wendtieae); loculicidal nature of capsule (present also in Balbisia and Wendtia, carpels ventrally dehiscent in Dirachma, otherwise mericarps which separate from the floral axis); presence of endo- sperm (scanty or absent in Geraniaceae); and nature ofleaves (opposite and simple in Viviania, mostly not opposite and often palmatifid in the Geraniaceae).Segregation of Viviania from Geraniaceae requires decisions on whether Ledocarpaceae (Wendtieae as a tribe: Balbisia, Rhyncotheca, and Wendtia), Biebersteiniaceae (Biebersteinia) and Dirachmaceae (Dirachma) should also be segregated.
During my travel in Chile in 1982, I collected material of Viviania crenata (Hook.)G. Don.This has been supplemented by material available from herbarium specimens of V. laxa Phil.and V. spinescens Presl.Viviania can be described as a subshrub bearing branches attached to a woody caudex.Branches persist variously; the bases of some may become woody for several years.The wood of branches may differ somewhat from that of the caudex, so one should not regard a wood description based upon one part as applying to the other.
In addition to availability of material, study of Viviania wood is prompted by the desirability of understanding woods other than those of arboreal species.
Geraniaceae are a non woody group typically; the fact that Geraniaceae have rayless woods (Barghoorn 1941;Carlquist 1986) suggests that they, like other groups with rayless woods, may represent phylesis toward woodiness from an essentially herbaceous ancestry (Carlquist 1970).The present study examines whether or not all Geraniaceae s.l.follow this pattern.
The study of only three species of Viviania may seem to represent an inadequate sampling of the genus.In fact, most species provide insufficient wood for convenient study, and those represented here are among the woodiest.The ecological range represented here is probably nearly maximal for the genus, since V. spinescens represents a xeric area, whereas V. cuneata comes from an only moderately dry area (all Viviania localities could be described as relatively dry; although weather data for the localities are not available, the vegetation, compared to that oflocalities in California where rainfall records are available, suggests precipitation of between 25 and 50 em per year).About half of the species in the genus belong to what could be termed the "V.rosea Hook.complex" and were segregated from V. rosea by Knuth (1912) and others; these species do not represent any marked differentiation from each other in growth form, ecology, or other factors that would tend to be reflected by differences in wood anatomy.

MATERIALS AND METHODS
Wood samples were available in dried form.The material of V. crenata represents aboveground stems about 7 mm in diameter, collected in scree areas in the Parque National "La Campana," along the Cuesta de Ia Dormida road west ofTiltil, north of Santiago, Chile.The material of V. laxa represents aboveground stems 8 mm in diameter; it comes from the "Cuesta del Espino" between Combarbala and Illapel, Coquimbo Prov., Chile.The wood of V. spinescens is from a woody caudex, 1.5 em in diameter, at ground level; that specimen was collected on the Llano de Junalillo, 2600-2700 m, Aconcagua Prov., Chile.
Voucher specimens for all collections are located at RSA.The monograph of Knuth (1912) was used for identification of specimens.
Wood samples were boiled and stored in 50% ethyl alcohol.All samples proved suitable for sectioning without prior softening; they were sectioned on a sliding microtome.Presence of starch was established in V. spinescens sections by means of staining with IKI.Permanent slides were made of wood sections of all three species by means of staining with a safranin-fast green combination and mounting in Coverbond (Piccolyte).Macerations were prepared with Jeffrey's Fluid and stained with safranin.Quantitative feature means were obtained from average of 25 measurements except in vessel wall thickness, fiber-tracheid wall thickness, and fiber-tracheid diameter, where a typical condition was selected.
VIVIANIA SPINESCENS, Ricordi 2912.Growth rings present, vessels wider in earlywood.Vessels circular to oblong in transectional outline.Mean vessel diameter, 36 ~-tm.Mean number of vessels per mm 2 , 223.Mean number of vessels per group, 1.76; some vessels in radial multiples.Mean vessel wall thickness, 2.6 ~-tm.Mean vessel element length, 144 ~-tm.Perforation plates simple.Lateral walls of vessels with pits 2-4 ~-tm in diameter.Pit apertures interconnected by grooves; additionally, pairs of faint thickenings are present beside grooves in some vessels.Numerous thin-walled spherical tyloses present in vessels.All imperforate tracheary elements are fiber-tracheids.Mean fiber-tracheid diameter, 28 ~-tm.Mean fibertracheid wall thickness, 2.3 ~-tm.Mean fiber-tracheid length, 193 ~-tm.Fiber-tracheid pits about 2 ~-tm in diameter, borders present but less conspicuously present than in the other species.Starch abundantly present in some ofthe fiber-tracheids.Axial parenchyma absent.Rays absent.Storying variously evident but not strongly marked.SYSTEMATIC CONCLUSIONS Knuth (1912) recognizes five tribes of Geraniaceae: Geranieae (all genera except those listed following); Biebersteinieae (Biebersteinia); Wendtieae (Balbisia, Rhynchotheca, Wendtia); Vivianieae (Viviania); and Dirachmeae (Dirachma).Dahlgren ( 1980) raised all of these to the level of family (Ledocarpaceae applies to Wendtieae when recognized as a family).Thome (1983) gives familial status to two of these (Vivianiaceae and Ledocarpaceae) but retains Dirachmoideae and Biebersteinioideae as subfamilies.Vivianiaceae may be the most distinctive of these on the basis of wood because of presence of borders on pits of imperforate tracheary elements and absence of axial parenchyma (Balbisia has axial parenchyma: original observation based on B. peduncularis [Lindl.]D. Don, Ricardi 4347, RSA).Presence of pits on imperforate tracheary elements of Viviania was reported by Metcalfe and Chalk (1950).The borders are most prominent, among the species studied here, on fiber-tracheids of V. taxa.Endosperm presence, like pit border presence in fiber-tracheid in Viviania, can be considered a primitive feature.Most workers, however, would consider the polyporate pollen condition, as well as the absence of axial parenchyma, to be specialized conditions in Viviania.Wendtieae (Ledocarpaceae) have simple pits on imperforate tracheary elements and do have axial parenchyma (original observation, Batbisia peduncutaris), but they have polyporate or nonaperture pollen (Erdtman 1952).The capsular fruit types of the subfamilies or tribes other than Geranieae were mentioned in the Introduction; these fruit types may be considered less specialized than the mericarps of Geranieae and Biebersteinieae.
One can conclude that of the five tribes of Geraniaceae recognized by Knuth (1912), also cited as five families by Dahlgren (1980), Vivianiaceae is the most distinctive one.Wendtieae (Ledocarpaceae) is close morphologically to Vivianiaceae, since both groups are native to southern South America.Dirachma (endemic to Socotra Island) is isolated geographically and may be nearly as distinctive as Viviania, but nothing has been reported on its anatomy to date.
The presence of rayless wood, reported here for Viviania, has also been found in Batbisia and Wendtia (Metcalfe and Chalk 1950).Rayless wood has been reported in Geraniaceae s.s.(Barghoom 1941, Metcalfe andChalk 19 50, Carlquist 1986).The fact that this feature, unusual in dicotyledons at large, is present in all of the geranioid groups, suggests the closeness of these entities.There seems little doubt that Viviania is related to Geraniaceae; the only remaining question is how to demonstrate the degree of taxonomic affinity that Viviania represents.The problem in segregating Vivianiaceae from Geraniaceae is that Dirachmaceae and Ledocarpaceae would be only slightly less justifiable as segregants, Biebersteiniaceae even less defensible.The presence of these taxa with varying degrees of difference from Geraniaceae s.s.lessens the merit of segregation of Viviania, which very likely would readily be recognized if the other subfamilies (or families) did not represent smaller discontinuities, involving some of the same characters as those that distinguish Viviania.

ECOLOGICAL CONCLUSIONS
If one calculates the ratio "Mesomorphy" (Carlquist 1977) for the Viviania collections studied here, one finds the values: V. crenata, 11. 7; V. taxa, 2.8; V. spinescens, 23.2.These are all of the same order ofmagnitude and reflect the dry habitats occupied by Viviania.The somewhat higher value for V. spinescens may be related to the fact that an underground caudex was studied in that species, whereas aboveground branches were studied in the others.Underground portions of dicotyledons tend to have more mesomorphic wood structure than aboveground portions.Xeromorphy is shown in Viviania about equally by all three of the features represented by the Mesomorphy ratio-vessel diameter, number of vessels per mm 2 of transection, and vessel element length.The number of vessels per mm 2 in V. taxa, 1001, is exceptionally high, and indicates a high degree of xeromorphy.
The number of vessels per group in Viviania is not exceptional, but it probably does represent a degree of adaptation to xeromorphy.The occurrence of helical