FRESH-WATER ALG^ OF THE UNITED STATES. 35 



In regard to the temperatures given, and the observation as to the presence of 

 animal life in the thermal waters, Mr. William Gabb, of the State Geological 

 Survey, states "that he has visited the locality, knows Mrs. Partz very well, and that 

 whatever she says may be relied on as accurate. 



The color of the dried specimen varies from a very elegant bluish-green to dirty- 

 greenish and fuscous-brown. After somewhat prolonged soaking in hot water, the 

 specimens regained apparently their original form and dimensions, and were found 

 to be in very good condition for microscopical study. 



The plant in its earliest stages appears to consist simply of cylindrical filaments, 

 which are so small that they are resolved with some difficulty into the component 

 cells by a first-class one-fifth objective. Fronds composed entirely of filaments of 

 this description were received. Some of these were marked as " first forms," and 

 as having grown in water at a temperature of 160° Fahr. Probably these were 

 collected immediately over the spot where the heated water bubbled up. At this 

 temperature, if the collection made is to be relied on as the means of judging, the 

 plant does not perfect itself. To the naked eye these "first forms" were simply 

 membranous expansions, of a vivid green color and indefinite size and shape, 

 scarcely as thick as writing-paper, with their edges very deeply cut and running 

 out into a long, waving, hair-like fringe. Other specimens, which grew at a much 

 lower temperature, exactly simulated those just described, both in general appear- 

 ance and microscopical characters. These, I believe, were the immature plant. 



The matured fronds, as obtained by the method of soaking above described, were 

 " gelatinous membranous," of a dirty-greenish or fuscous-brown at their bases, and 

 bright green at their marginal portions, where they were deeply incised and finally 

 split up into innumerable hair-like processes. Proximally they were one, or even 

 two, lines in thickness, distally they were scarcely as thick as tissue paper. Their 

 bases were especially gelatinous, sometimes somewhat translucent, and under the 

 microscope were found to have in them only a few distant filaments. 



Two sets of filaments were very readily distinguished in the adult plant. The 

 most abundant of these, and that especially found in, the distal portions of the 

 fronds, were composed of uniform cylindrical cells, often enclosed in a gelatinous 

 sheath. The diameter of such filaments varies greatly; in the larger the sheaths 

 are generally apparent, in the smaller tjiey are frequently indistinguishable. 



In certain places these filaments are more or less parallel side by side, and are 

 glued together in a sort of membrane. It is only in these cylindrical filaments 

 that I have been able to detect heterocysts, which are not very different from the 

 other cells; they are about one-third or one-half broader, and are not vesicular, but 

 have contents similar to those of the other cells. In one instance only was I able 

 to detect hairs upon these heterocysts. 



The larger filaments are found especially near the base and in the other older 

 portions of the frond. Their cells are generally irregularly elliptical or globose, 

 rarely are they cylindrical. They are mostly of an orange-brown color; and there 

 exists a particular gelatinous coating to each cell rather than a common gelatinous 



