MARSILEACEAE. 5 



portion quadripinnate below, gradually simpler above; sporangia numerous, 

 crowded, bright yellow. Rare, in wet meadows, near Moscow, Idaho. 



Family 3. MARSILEACEAE. 



Plant perennial, herbaceous, rooting in the mud, with slender 

 creeping rootstock and four-foliolate or filiform leaves ; sporangia 

 borne within closed receptacles (the sporocarps) which arise 

 from the rootstock near the leafstalks or are consolidated with 

 them; spores of two kinds, large ones (megaspores) and small 

 ones (microspores), both contained in the same sporocarp. 



10. MARSILEA. 



Marsh or aquatic plants; leaves slender petioled, quadri- 

 foliolate, commonly floating on the surface of shallow water; 

 sporocarps ovoid or bean-shaped, peduncled and rising from the 

 petiole or from the rootstock at the base of the petiole, composed 

 of two vertical valves having several transverse compartments 

 (sori) in each valve; also provided inside with a ring which at 

 the opening of the valves swells and tears the sori from their 

 positions; sori composed of both megasporangia and micro- 

 sporangia. 



Marsilea vestita Hook. & Grev. Rootstock slender, creeping; leaves 

 more or less pubescent with white hairs; petioles slender, 4—12 cm. long; 

 leaflets deltoid-obovate, 4-12 mm. long, mostly entire; sporocarps solitary 

 on the stalks, 4-8 mm. long, 3-S mm. wide, with a short raphe, a short blunt 

 lower tooth, and an acute upper one, densely pubescent with white appressed 

 hair-like scales; sori 6-11 in each valve. Common on the banks of ponds, 

 frequently aquatic, the leaves floating on the surface in spring and early 

 summer. 



Class II. EQUISETINEAE. 



Plants rush-like with hollow jointed stems rising from 

 subterranean rootstocks; sterile leaves reduced to minute 

 scales, whorled, forming sheaths at the joints; fertile leaves 

 forming a short spike terminating the stem; epidermis 

 rough. 



Family 4. EQUISETACEAE. 



Branches, when present, whorled; sporangia one-celled, clus- 

 tered under the scales of the terminal cone-like spikes; spores of 

 but one kind furnished with narrow ribbon-like appendages 

 (elaters) attached at the middle, coiling around them when 

 moist and spreading in the form of a cross when dry and mature ; 

 epidermis impregnated with silica, rough. 



