ENGELMANN THE GENUS ISOETES IN N. AMERICA. 379 



4. I. ECHiNOSPORA, Durieu. One of the smaller species with 10 to 30 

 or 40 soft bright green or sometimes reddish leaves, gradually and regu- 

 larly tapering from a thick base to a very slender elongated point abso- 

 lutely without stomata, 2 to 4 or sometimes 5 inches long ; sporangia 

 orbicular to broadly oval, unspotted, with a narrow velum ; macrospores 

 0.40 to 0.50 mm. thick, densely covered with delicate, erect, truncate, or 

 slightly forked spinules; microspores 0.030 to 0.034 "im. long, almost 

 smooth.— Bull. Bot. Soc. Fr. 8, 164. 



Only in Europe from Northern Italy to Germany, France and England, 

 extending to Lapland and Iceland, but apparently not in America. 



In this country we have a series of forms which have been distinguished 

 by eminent authority, especially on account of the presence of stomata so 

 various in number and often so difficult to discover, and of a slight differ- 

 ence in the form and size of the microscopic spinules which cover the ma- 

 crospores. I have thought best to unite them specifically with the Euro- 

 pean type, though it seems strange that in the European plant stomata 

 should be absolutely absent, and it must remain subject to individual judg- 

 ment, if not doubt, which view ought to be preferred. Nearest to the Eu- 

 ropean true /. cchinosp07-a stands the var. Brauvii and the other extreme 

 is var. muricata, wide-ranging forms of a single type. The same difficul- 

 ties, the same doubts, and the same solution, we find in studying some 

 foreign forms and especially those allied to /. velata of the south of Europe. 



* * Stomata few. 



I. ECHINOSPORA, var. Braunii, Engelm. Rather small, with J3 to 15 

 green or reddish-green erect or spreading, rather short (3 to 6 inches long), 

 tapering, soft leaves, generally with few stomata towards the tip only; 

 sporangia orbicular to broadly elliptical, spotted, generally k or even | 

 covered by a broad velum ; macrospores 0.40 to 0.50 mm. thick, rarely a 

 little longer, covered with broad, refuse spinules, sometimes somewhat 

 confluent, and then dentate or incised at tip ; microspores 0.026 to 0.030 

 mm. long, smooth. — Gray Man. 1. c. /. Braunii^ Durieu 1. c. 11, p. loi. 



The most common species of our flora from New Jersey and Pennsylva- 

 nia, northward and northwestward, sometimes on gravelly soil, at other 

 places reported from soft mud, in ponds or slow-running streatns, also 

 near the banks of larger lakes or under the influence of tidewater, nor- 

 mally submerged from a few inches to several feet, in dry seasons some- 

 times getting out of water; associated with Brtocaulon septangulare. 

 Lobelia Dortmana, Spargatitum, Scirpus, Eleocharis, etc. New Jersey : 

 in tidewater of Tom's river, a slender long-leaved form, C. F. Parker^ 

 C. E. Smith, and others; in a lake in Morris Co., T. C.Porter. Pennsyl- 

 vania: Montrose, Susquehanna Co., A. P. Garber ; Great Lake, Pocono 

 Mountain, Po/'^ertf- Catiby ; Presque Isle, Erie, vl. Z'. Garber. New York: 

 Catskill Mountains in the lake near the hotel, G. W. Clinton; Round Lake 

 above Bolton, west of Lake George, on white sand, and in Lake Placide, 

 L. Lesquereux; Luzerne Lake and in Niagara river below Buffalo, G. W. 



