The Ferns of Washington 77 



long, slender, bast-bundles 4, stomates present. Mega- 

 spores .290 -.350 mm. in diameter, covered with sliort 

 blunt slender spinules, the equator also beset with these 

 points. Microspores papillose or sparingly spinulose, 

 white, .026-.031 mm. long. The smallest American 

 species. — Washington (Spokane County). 



2. Isoetes Howellii Engelm. 



Plant submerged in winter, in summer often only 

 partly so; leaves 6-50, 2-8 in. long, with numerous sto- 

 mates and 4 bast bundles. Megaspores .250 -.500 mm. 

 in diameter, dark gray or black, covered with low blunt 

 isolated or confluent crests. Microspores .020-. 030 mm. 

 long, light brown, covered with low blunt tubercle- or 

 spines. — AYasIiington to California and Idaho. 



3. Isoetes Nuttallii A. Br. 



Plant terrestrial, growing in wet plac( ■ Leaves 2-9 



in. long, with 3 peripheral bast bundles. Sporangia 



covered by indusia. Megaspores small, .250-. 500 mm. 



in diameter, white or light gray, of glassy lustre, marked 



by small regular warts. Microspores papillose, brown, 



.025-. 028 mm. long. — California to British Columbia and 

 Idaho. 



4. Isoetes paupercula (Engelm.) Eat. 



Plant submerged. Leaves 5-20, 2-5 in. long, thin, 

 without stomates, peripheral bast-bundh 8 wanting. 

 Megaspores with irregular ridges. Microspores .026 



-.036 mm. long, granulate.— Washington to California 



and Colorado. 



5. Isoetes Piperi Eat. (Plate 3, Fig. 3.) 



Plant submerged. Stomates none. Megaspores with 



low, distinct warts. — Washington. 



6. Isoetes Bolanderi Engelm. 



Plant submerged. Leaves 5-25, erect, soft, bright 

 green, tapering to a fine point, thin-walled, with few 



