52 On the North American Species of Isoétes and Marsilea. 
Arr. VIL—On the North American Species of Isoétes and 
Marsilea; by Prof. A. Brauy.—Communicated by Dr. G. 
ENGELMaANy. 
Dr. A. Bravn, since last spring Professor of Botany at the Univer- 
sity of Freiburg, Germany, has from time to time eémmunicated 
to me the results of his investigations on the cryptogamous plants 
of this country. His notes on Chare and Fiquiseta have been 
published in a former number of this Journal, (January, 1844.) 
am now enabled to offer some remarks of his on the above named 
genera of rhizocarpous plants. ‘Those on Marsilea have been 
furnished in manuscript; the paper on Isoétes was published in 
the “Flora, oder Bot. Zeitung,” No. 12, 1846.—G. FE. 
The species of Isoétes hitherto discovered in the United States, 
have been considered identical with the European I. lacustris, 
Liun., especially one found in Pennsylvania. But this, as well as 
two others obtained from North America, on careful examination 
yc the species examined by me may be distinguished by the 
uillerent size and surface of the spores. . Other characters are to 
be found in the shape of the rhizoma, and in the shape and sec- 
tion of the leaves. ‘These last can be well examined only in 
living plants; the shape of the rhizoma may also be seen in dried, 
found only under water (1. lacustris, I. Slaccida, I. a); 
others grow in shallow water, or on wet places which sometimes 
become quite dry (J. setacea, I. Engelmanni, I. riparia) ; others 
again grow on perfectly dry hills (I. Durieni, I. hystrix). I. se 
tacea of the South of Burope is also often found in dry places ; 
near Erejus it forms large patches of a beautiful green color at 
the foot of walls; and I have cultivated it in flower pots, which 
were kept moderately moist. _ I will here take occasion to remind 
travelers and collectors, who may meet with species of this genus. 
that all of them are very tenacious of life, much like bulbous 
