1922] 



PFEIFFER — MONOGRAPH OF THE ISOETACEAE 191 



Corm 2-lobed; leaves 8-26, 3-10 cm., rarely 15 cm., long, medi- 

 um fine, erect or somewhat spreading, taper-pointed, broadly 

 winged for twice length of sporangium; peripheral strands and 

 stomata lacking; ligule short, triangular, ovate; sporangia 4-5 

 mm. long, with variation in width of velum from 1/3 to 2/3 of 

 sporangium ; megaspores white, 540--800 |j in diameter, marked 

 with points or tubercles and short ridges, sometimes slightly 

 serpentine; microspores 29-35 u, rarely 42 u, long, papillose. 



Distribution : Washington. 



Specimens examined: 



Washington: Seattle, 11 July, 1889, Piper (Mo. Bot. Gard. 



Herb.); Seattle, 11 July, 1889, Smith (Mo. Bot. Gard. 

 Herb.) ; Lake Washington, near Seattle, 11 July, 1889, Piper 

 & Smith 651 (N. Y„ Bot. Gard. Herb.); Green Lake, King 

 Co., 12 July, 1835, Piper 2317 (Mo. Bot. Gard. Herb, and 

 N. Y. Bot. Gard. Herb.), type; mostly submerged in clear 

 lake, Five Mile Lake, Tacoma, 3 October, 1902, Flett 2034 

 (Mo. Bot. Gard. Herb., U. S. Nat. Herb., and N. Y. Bot. 

 Gard. Herb.); Lake Washington, Seattle, August, 1907, 

 Piper & Hungate (U. S. Nat. Herb.); submerged, Lake 

 Crescent, 20 August, 1911, Webster (IT. S. Nat. Herb.); in 

 Green Lake, near Seattle, June, 1891, Piper 1102 (N. Y. Bot. 

 Gard. Herb.). 



It is possible that /. Piperi Eaton and /. occidentalis Hend. 

 may be more closely related than as adjacent species. A slight 

 difference in habit of the leaves (more gradual tapering in /. 

 occidentalis, coupled with greater length), a difference in spore 

 sizes, with /. Piperi tending to show the larger megaspores and 

 smaller microspores, and a simpler form of sculpture on /. Piperi 

 compared with the anastomosing ridges of /. occidentalis, and a 

 tendency toward wider velum in /. Piperi, serve to distinguish 



these two submerged species. 



Sect. 4. Reticulatae 



4. Reticulatae. Forms with 2-3 lobed corms; producing 

 megaspores evidently reticulate, at least on basal face; micro 

 spores smooth or rough. 



