16 Joint Bitxetix 3 



mountain brooks, where it occurs occasionally, and seems more or less 

 confined to shaded pools, where it is attached to rocks in under water. 

 Drapemaldia is one of the most beautiful of our algae, and like some of 

 our orchids, seems to seclude itself in the heart of the wildest woods. 



The phylum Zj/gophyceae. the yellow-green or conjugate algae, in- 

 cludes some of our commonest algae. The group as a whole is charac- 

 terized by unbranched filaments consisting of a single series of 

 cylindrical cells. The plants are sluggish, typical of still waters, free- 

 floating, and for the most part yellow-green in color. The reproduction 

 is by the fusion of two cells in adjacent filaments following the forma- 

 tion of a connecting tube, and this fusion gives rise to a zygospore, 

 from which the group takes its name. 



Spirogyra is the most noticeable of the genera in this group, and 

 about a dozen species are reported from Vermont. The green scums 

 on still pools and the large green masses resting on submerged rocks 

 are often made up chiefly of species of Spirogyra. The name of the 

 genus is suggested by the one or more spiral chloroplasts which wind 

 about within each cell. Spirogyra is one of the innocent recipients of 

 that non-botanical term "frogspit." 



In Zygnema we have a genus of filamentous plants similar in habit 

 to Spirogyra. and differing chiefly in having two star-shaped chloro- 

 Dlasts within each cell instead of the spiral bands. While Zygnema is 

 not so widely represented in Vermont, there are several species, and 

 it is not at all uncommon. 



The desmids comprise a subdivision of this group in which the 

 individual cells are organized into symmetrical halves, each contain- 

 ing a chloroplast. The filaments usually break up into single cells, 

 and some are motile. The desmids exhibit a wonderful variety of 

 form, and are often very beautiful. They are found free-floating in 

 quiet pools or entangled with other algae. 



The diatoms comprise a group of plants characterized by rigid 

 silicate walls and a box-like structure, typically isolated but some- 

 times as a filament, for the most part yellow-brown in color and mov- 

 ing about through the water by means of pseudopodia. The silicate 

 walls of the diatoms are marked by minute transverse lines. The 

 desmids and diatoms are such varied groups of plants, and comprise so 

 many species — some 10,000 — that in the study of the writer they have 

 been passed by without comment. They abound in all waters and moist 

 soils. 



The Siphonophyt eae or tube algae are typically aquatic green 

 plants, filamentous and branching, and composed either of segments or 



