ENGELMANN THE GENUS ISOETES IN N. AMERICA. 386 



a tributary of Coosa river, Floyd Co., in slow-flo-wing water about a foot 

 deep. A. W. Chaftnan. 



The trunk of this species is larger than I have seen it in any other, and 

 more variable in form ; sometimes it is quite flat and over one inch wide, 

 especially in var. valida, or it :s thick; and I have seen it even twice as 

 high as it was wide, 4J lines wide in the largest transverse diameter and 7, 

 lines high ; this, however, is a very unusual form. The plant is submerged 

 in spring with the leaves partly floating; later, when the water recedes, 

 the older leaves are spread out on the mud, but the later growth becomes 

 erect; V2S. gracilis is often more or less submerged, and its weakly devel- 

 opement is probably owing to this circumstance, while var. valida is the 

 stoutest form we have, and one of the stoutest in the whole genus, perhaps 

 only /. Malinvcriana of the rice fields of I^ombardy surpassing it. Avery 

 small form, only 5 inches high, has been collected in a springy place on a 

 rocky hillside near Wilmington, Del., by A. Commons, otherwise not dis- 

 tinct. The Georgia variety, characterized by its larger spores, ought to be 

 further studied. In my Missouri specimens I find, among many of the ordi- 

 nary type with white sporangium, a few where this organ is uniformly 

 brown, not spotted. The dissepiments of the leaves consist, the median 

 of 3 to 4 and the transverse one of 2 to 3 layers of cells. The well marked 

 reticulation of the macrospores is formed of very thin fragile laminae, not 

 of thick ridges as in some other species. 



10. I. HowELLii, Engelm. n. sp. Middle sized, leaves (10 to 25) bright 

 green (5 to 8 inches long) with thick dissepiments; sporangium oval {i^ 

 to 2\ lines long), unspotted, 5 to i covered by the velum ; subulate ligula 

 as long as sporangium; macrospores 0.43 to 0.48 mm. in diam., rough, 

 with prominent rounded single or sometimes confluent tubercles. 



On border of ponds at the Dalles of the Colurftbia, Oregon, J. d- T. jf. 

 Howell, iSSo, not quite mature in June. — I insert this species which has 

 just been coinmunicated to me through the kindness of Mr. G. E. Daven- 

 port, while the manuscript is in the hands of the printer; this must excuse 

 some discrepancies in the foregoing pages, where no reference could be 

 made to it. The new species is distinguished from the similar /. Bolatt- 

 deri by the longer leaves, larger more prominently marked macrospores, 

 and especially by the distinct peripheral bast-bundles, which place it near 

 the foregoing one, by the thick dissepiment consisting of 4 to 6 layers of 

 cells, and by the unusually narrow and long ligula; the tubercles of the 

 spores are quite prominent, as high as they are wide, rounded at top ; 

 microspores light brown, smooth. — Among the specimens of this species, 

 and probably collected with it, I find a single one similar in the structure of 

 the leaf, but without a trace of a velum, the sporangium being entirely 

 naked and only attached by the median line to the leaf base ; it is unfortu- 

 nately immature, and can only be indicated as a probably new species, 

 /. nuda. This would not be the first instance of two species growing 

 together in the same pond or lake ; in Mystic Pond we find /. Tuckermani 



iv — 2 — 13 



