24? 20. Isoetes. 2. LYCOPODIACEiE. PLend.cr . 
Isoetes lacustris, Lake quillwort. 
Leaves awlshape, halfround. 
Subularia vulgaris erecta, folio rigidissimo, Raii Syn. 306, 1. 
Calaniaria folio breviore et compresso, Dill. M. 540. 
Isoetes lacustris, Lin. S. P. 1563. 
Bottom of alpine lakes; perennial; May and June. 
Root tuberous, with numerous fibres; fronds numerous, 
4 to 6 inches high, simple, four-celled, jointed, dilated at 
the base, membranaceous, bearing fruit in their inside, of 
two sorts, a. in the internal base of the frond, solitary ; 
b, in the external base of the frond, size of a pea, roundish, 
rather compressed, membranaceous, two-celled, many 
seeded; seeds small, shagreened. 
|3. gracilis. Leaves long, slender. 
Calamaria folio longiore et graciliore, Dill. M. 541. 
y.fragilis. Leaves very brittle, slender, pointed, trans- 
parent ; pores numerous, minute. 
Subularia fragilis, folio longiore et tenuiore. Raii Syn. 307,3. 
Fam. III. 3. M A R S I L E A C E 7E . Brown. Rhizospermee , 
De Candolle. 
Fructifications radical ; involucrum spherical, leathery, or 
membranaceous, not opening; seeds many. — Aquatic herbs. 
21. PILULARXA. Vaillant. FI. Par. 159. Peppergrass. 
Involucrum solitary, subsessile, globular, leathery, four- 
celled.— Young leaves rolled up like those of ferns. 
Pilularia globulifera. Pillbearing peppergrass . 
Leaves threadlike. 
Graminifolia palustris repens, vasculis granorum piperis semulis, Raii 
Syn. 136. 
Pilularia globulifera, Lin. S. P. 1563. 
Pillwort. 
In inundated gravelly places; perennial; June, July. 
Stem creeping, rooting ; involucra axillary, downy, 
brown, closed, four-celled, lined with sexual organs ? an- 
thers? above, yellow, clubshaped; germens? below, round- 
ish, whitish. 
