I first observed Scleria lithosperma a few months ago, on May 31, 2012, in Key Largo, Florida. This is the only Scleria species listed as Endangered in Florida. Including S. lithosperma, I’ve now observed nine of the ten Scleria species known from Florida. Scleria is a genus belonging to the monocotyledonous family Cyperaceae. All Scleria species of Florida are native here, except for Scleria lacustris.
The fruit of all Scleria species is an achene (as is true for all other species of Cyperaceae). An achene is a dry, indehiscent, one-seeded, fruit. Species of Scleria, like species of other cyperaceous genera, are distinguished from one another largely according to features of their achenes. All ten of our Scleria species have white achenes (an atypical feature among Florida Cyperaceae, overall) and their achenes are minute - ranging, collectively, from one to four mm long. Because the achenes are so small, the beginner requires a microscope to see them clearly and to identify Scleria plants to species.
Florida species of Scleria appear, superficially, grass-like and weedy, and the average person would consider them unremarkable. Yet, their achenes appear unique and beautiful under the microscope. I’ll now review selected features of the achenes. While doing so, I’ll refer to the handout which I’ve distributed today. 1
- Shape.--The achenes range from spherical (S. ciliata) to ovoid (S. triglomerata) to fusiform (S. georgiana).
- Surface.—The achene surface may (a) be smooth (S. triglomerata), (b) exhibit longitudinal ridges (S. georgiana), (c) be reticulate (S. reticularis), or have different ornamentation (S. ciliata).
- Hypogynium.—A hypogynium occurs in certain but not all species (e.g., it is absent in S. lithosperma). The hypogynium is a discrete structure which adheres to the base of the achene. For example, in S. triglomerata the hypogynium appears as a roughened donut, whereas, in S. reticularis it exhibits three prominent lobes which clasp the base of the achene.
- Tubercles.—These are sometimes present. In the drawings of S. ciliata the tubercles are the rounded objects situated between the achene and the (pancake-like) hypogynium.
I’ll now consider the nine (of ten) species that I’ve observed so far in Florida. They are the following.
- Scleria lithosperma.—this is the Endangered species that I observed recently in Key Largo. I’ve seen it growing under power lines and in adjacent tropical hardwood hammock. Scleria lithosperma is one of three Florida species that have verticillate inflorescences. In a verticillate inflorescence, the central inflorescence axis bears flower clusters at intervals along its length.
- Scleria baldwinii.—I’ve found this species in Collier Co., Lee Co., and the Florida Panhandle.
- Scleria ciliata.—A rather abundant species with a number of varieties; I’ve found it in Collier Co. (including the Naples Botanical Garden) and Lee Co.
- Scleria distans (Scleria hirtella).—I’ve found this species in Lee County and in the Florida Panhandle; it exhibits verticillate inflorescences.
- Scleria georgiana.—I’ve found this species in Collier Co. and Lee Co.
- Scleria lacustris.—I’ve found this species in Lee Co. It is Florida’s only exotic species. It grows in wetlands and elicits concern as an invasive species. Ranked according to plant height, it is among Florida’s largest species. The inflorescence is a panicle - an unusual inflorescence type among Scleria species of Florida.
- Scleria reticularis.—I’ve found this species in Collier Co. and Lee Co., in wetlands.
- Scleria triglomerata.—I’ve found this species in Collier Co. (disturbed scrubland on Marco Island) and Lee County.
- Scleria verticillata.—I’ve found this species in Collier Co. and Lee Co.; it exhibits verticillate inflorescences.
1 The illustrated handout is a compilation of illustrations from the following source:
Godfrey, R. K., and J. W. Wooten. 1979. Aquatic and wetland plants of southeastern United States.Monocotyledons. The University of Georgia Press, Athens, GA. 712 p.