SELAGINELLACE^E. 699 



covered by the velum, the free part pale and unspotted ; both kinds of spores 

 the largest of our species; macrospores (0.32- 0.38" wide) covered with short 

 and twisted crested ridges, which often anastomose ; microspores (0.017 - 0.020" 

 long) smooth. Mountain lakes, Penn., N. Y., and New Eng. to Lake Supe- 

 rior, and northward, often with n. 3. (Eu.) 



2. I. Tuckermani, Braun. Leaves (10-30, 2 -3' long) very slender, 

 awl-shaped, olive-green, the outer recurved ; sporangium ovoid or circular, the 

 upper third covered by the velum, the free part sometimes brownish-spotted ; 

 macrospores (0.22-0.28" wide) on the upper segments covered with parallel 

 and anastomosing ridges, the lower half reticulated; microspores (0.013- 

 0.015" long) smooth or very delicately papillose. Mystic and other ponds 

 near Boston, together with the next (Tuckerman, W. Boott). 



3. I. echinospora, Durieu. Leaves slender, awl-shaped ; sporangium 

 ovoid or circular; macrospores (0.20-0.25" wide) beset all over with small 

 entire and obtuse or slightly forked spinules. (Eu.) In this European form, 

 the leaves are very slenderly attenuated (3 -4' long), the upper margin of the 

 sporangium only is covered with the narrow velum, the free part is unspotted, 

 and the slightly papillose microspores are larger (0.015-0.016" long). 



Var. Bratmii, Engelm. Leaves (15-30 in number, 3-6' long) dark and 

 often olive-green, straight or commonly recurved, half or two thirds of the 

 sporangium covered by the velum, the free part often with light brown spots ; 

 macrospores as in the type ; microspores smaller (0.013-0.014" long), smooth. 

 (I. Braunii, Durieu.) Ponds and lakes, New Eng. to N. Y., Penn., Mich., and 

 northward, often with the two preceding. Frequently with a few stomata, 

 especially in Niagara specimens. 



Var. roblista, Engelm. Stouter; leaves (25-70, 5- 8' long) with abun- 

 dant stomata all over their surface ; velum covering about one half of the large 

 spotted sporangium ; macrospores 0.18 - 0.27" wide. Lake Champlain, north 

 end of Isle La Motte (Pr ingle). 



Var. muricata, Engelm. Leaves (15-30, 6-10' long) straight or flac- 

 cid, bright green ; about one half of the almost circular sporangium covered by 

 the velum, unspotted ; macrospores (0.22 - 0.27" wide) with shorter and blunter 

 spinules ; microspores as in the last variety, or rarely spinulose. (I. muricata, 

 Durieu.) In some ponds north of Boston ( W. Boott). 



Var. Boottii, Engelm. Leaves (12-20, 4-5' high) awl-shaped, stiffly 



erect, bright green, with stomata ; sporangium as in the last ; macrospores as 



in the type, but a little smaller and with very slender spinules. (I. Boottii, 



Braun, in litt.) Pond in Woburn, near Boston, partly out of water ( W. Boott). 



* * Growing partly out of water, either by the pond drying up or by the receding 



of the ebb tide; leaves with stomata, and in n. 6 and 7 with four or more 



peripherical bast-bundles. 



4. I. saccharata, Engelm. Leaves (10- 15, 2-3' long) slender, olive- 

 green, curved ; sporangium small, ovoid, only the upper edge covered by the 

 velum, nearly unspotted; macrospores (0.20-0.22" wide) minutely tubercu- 

 late; microspores (0.012" long) papillose. On Wicomico and Nanticoke 

 Rivers, eastern shore of Maryland, between high and low tide ( Canby). 



5. I. riparia, Engelm. Leaves (15-30, 4-8' long] slender, deep green, 

 erect ; sporangium mostly oblong, upper margin to one third covered by the 



