24. 20. Isoetes. 2. LYCOPODIACE^. PI end. cr. 



Isoetes lacustris. Lake quillwort. 



Leaves awlshape, halfround. 



Subularia vulgaris erecta, folio rigidissimo, Raii Syn. 306, 1. 

 Calaniaria folio breviore ec compresso, Dill. M. 540. 

 Isoete:i lacustris, Lin. S. P. 1563. 



Bottom of alpine lakes ; perennial ; May and June. 



Root tuberous, with numerous fibres; //-o/zc/s 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 ; 

 h. in the external base of the frond, size of a pea, roundish, 

 rather compressed, membranaceous, two-ceiled, many 

 seeded ; seeds small, shagreened. 



^. gracilis. Leaves long, slender. 

 Calamaria folio longiore et graciliore. Dill. M. 641. 



y.fragilis. Leaves very brittle, slender, pointed, trans- 

 parent ; pores numerous, minute. 



Subularia fragilis, folio longiore et tenuiore. Rail Syn. 307,3. 



Fam. III. 3. MARSILEACE^. Brown. Rhizospermee, 

 De CandoUe. 



Fructifications radical ; involucrum spherical, leathery, or 

 membranaceous, not opening; seeds many. — Aquatic herbs. 



21. PILULARIA. Vaillant. Fl. Par. 15.9. Pepper grass. 



Involucrum solitary, subsessile, globular, leathery, four/- 

 celled. — Young leaves rolled up like those of ferns. 



Pilularia globulifera. Pillhearing pepper grass. 



Leaves threadlike. 



Graminifolia palustris repens, vasculis granorum piperis aemulis, 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 ? a?i- 

 thersP above, yellow, clubshaped; germens P below, round- 

 ish, whitish. 



