252 WOOD, ON SOME ALG^ FROM A 



were marked as " first forms/' and as having grown in Avater 

 at a temperature of 160° Fahr. Probably these were col- 

 lected immediately over the spot Avhere 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 colour and 

 indefinite size and shape, scarcely as thick as Avriting-j)aper, 

 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 de- 

 scribed, both in general appearance and microscopical cha- 

 racters. * 



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 wp into innumerable hair-like processes. Proxi- 

 mally 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 transculent, 

 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 ap)parent, in 

 the smaller they are frequently indistinguishable. 



In certain jolaces 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 colour; 

 and there exists a particular gelatinous coating to each cell 

 rather than a common gelatinous sheath to the filament. 



