702 SELAGINELLACEX.-—— MARSILEACEA. 
Sub-class II. Heterosporia. 
Order 1. SELAGINELLACE®, the Selaginella Order.—Cha- 
racter.—Terrestrial or water plants (fig. 1119), with branched 
slender stems, or the stems are corm-like (fig. 1119). Leaves 
sessile, small, and imbricate all round the stem or distichous, 
orinthe plants with corm-like stems tufted, long, and somewhat 
linear (fig. 1119). Sporangia of two forms, the larger called the 
macrosporangium or megasporangium (fig. 816), 2—4-valved, 
and containing 2—8 large spores (macrospores or megaspores) ; 
and the smaller or microsporangium (fig. 815), resembling that 
of the Lycopodiacex, and containing a number of small spores 
(microspores). (See pages 369 and 370.) The species of Isoétes 
are sometimes formed into a distinct order—the Isvétacex (see page 
370). They are here included in Selaginellacez. 
Distribution and Numbers.—They are found in all temperate 
and warm climates. There are 2 genera, and about 100 species. 
Illustrative Genera :—Selaginella, Beawv. ; Isoétes, Linn. 
Properties and Uses.—Unimportant. 
Order 2. MARSILEACE% or RuHiIzocaRPEH, the Pepperwort 
Order. —Character.—Aquatic herbs with small floating or 
creeping stems (fig. 1120), from which arise sessile (fig. 1120) or 
Fre. 1120. 
Fig. 1120. The Creeping Pillwort (Pilulavia globulifera). The stems are 
creeping, and bear numerous sessile leaves, which are circinate in verna- 
tion. The sporocarps are downy, and placed in the axils of the leaves. 
stalked leaves (fig. 366). Leaves with circinate vernation (fig. 
1120). Fructification at the base of the leaves (jig. 1120), and 
consisting of stalked valvular sporocarps (figs. 817, 819, and 
820) enclosing antheridia in which a number of small spores 
(microspores) are contained ( fig. 818), and sporangia (fig. 820, 5), 
both of which are either contained in the same cavity (fig. 817) 
or in separate sacs (fig. 820). (See pages 370 and 371.) 
