262 PHYLUM X. CALAMOPHYTA 
diameter. The epidermis is abundantly supplied with 
stomata. 
466. The Wedge-leaved Calamites (Class SpHENO- 
PHYLLINEAE) were Paleozoic herbaceous © 
ag plants of moderate dimensions, whose sporo- 
W phyte stems were solid, jointed, grooved ex- 
LE ' 2 ternally, and at the joints bore spreading 
whorls of wedge-shaped leaves. Their iso- 
_‘Spheno. Spores were borne in terminal cones com- 
posed of whorls of 1- or 2-sporangiate spor- 
ophylls. Sphenophyllum is the typical genus. 
467. In the Horsetails (Class EquisreTINEAE) of the 
present, the plant-body of the sporophyte 
consists of a hollow, elongated and jointed 
herbaceous stem, bearing whorls of narrow, 
united leaves, which form close sheaths; the 
stem is grooved, and is usually rough and 
hard from the large amount of silica depos- 
ited in the epidermis. tual Vena 
468. The branches, when present, are in ee 
whorls. Both the main axis and the branches are in 
most cases richly supplied with chlorophyll-bearing tis- 
sue; but in some of the species the stems which bear 
the spores are destitute of chlorophyll. All of the 
species have underground stems, which bear roots and 
rudimentary sheaths, and which each year send up the 
vegetating and spore-bearing stems. 
469. The Horsetails are perennial plants. In some 
species the underground portions, only, persist, the 
aerial stems dying at the end of each year; these are called 
the annual-stemmed species. In other species the 
aerial stems persist; they are hence known as perennial- 
stemmed. ; 
470. The epidermal cells are mostly narrow and 
