The inﬂorescence unit of Schoenus nigricans and S. ferrugineus consists of a zigzag axis and distichously arranged bracts, each of which may or may not subtend a bisexual ﬂower. Each ﬂower seems to terminate a lateral axis. These features have led to a controversy about the nature of the inﬂorescence unit, particularly whether it is monopodial or sympodial. It was often seen as a pseudospikelet composed of a succession of lateral axes, each subtended by the prophyll of the previous axis, as in a rhipidium. Many authors, however, consider the inﬂorescence units of all Cyperaceae to be indeterminate, racemose, actual spikelets. In our study, we present new SEM observations on the ﬂoral ontogeny of S. nigricans, corroborating a monopodial interpretation of the spikelet. Concaulescent growth of the ﬂower primordium and the spikelet apex explains: (1) the presence of a peduncle under the ﬂower, (2) the advanced development of the subtending glume compared to its own ﬂower primordium, and (3) the position of the distal glume with regard to the distal ﬂower primordium.
Vrijdaghs, Alexander; Goetghebeur, Paul; Smets, Erik; and Caris, Pieter
"The Schoenus Spikelet: a Rhipidium? A Floral Ontogenetic Answer,"
Aliso: A Journal of Systematic and Evolutionary Botany:
1, Article 15.
Available at: http://scholarship.claremont.edu/aliso/vol23/iss1/15