194 FRESH-WATER ALG^ OF THE UNITED STATES. 



have the transparent beak of the zoospore (pi. 18, fig. 2d). Inside of the cell 

 the androspore, as it is called, shows no cUia, but when it is set free by a more or 

 less complete solution of the cell wall, it assumes the form of the ordinary (Edogo- 

 nium zoospore, with a crown of cilia, whose vibrations soon cause it to dart through 

 the water. These androspores are of course much smaller than an ordinary 

 zoospore, and after a period of active motion, they attach themselves to the parent 

 filament, generally either on or near the sporangial cell. Their first life-actions, 

 after settling, are precisely like those of the zoospore, namely, dropping of the 

 cilia, enlargement of the smaller end into the so-called " foot," an elongation of 

 the general mass, and the secretion of an outer coating of cellulose. In this way 

 a peculiar-shaped, somewhat ovate cell is formed, which contains a great quantity 

 of rich protoplasm with mostly a small amount of chlorophyl. From siich cells are 

 developed the mostly two- or three-celled, perfect antheridia, which in gynandrous 

 CEdogonia are generally to be seen, during the period of fructification, in numbers 

 attached to the filament, mostly in the neighborhood of the sporangium. Their pro- 

 toplasmic contents are remarkable for the activity of their movements, and I have 

 seldom seen more beautiful and rapid cyclosis than they display — currents setting in 

 ail directions — particles actually brushing against one another (pi. 17, fig. 2h). 

 The sperihatozoids are formed in the distal cell, sometimes one, sometimes more. 

 In the species 0. mirahile. Wood, (pi. 18, fig. 2 g, 2 i) in which I have most 

 carefully studied their origin, two are produced in the single cell. This cell is in 

 the commencement of the process, although comparatively poor in chlorophyl, 

 crowded with a rich solid protoplasm, which divides into two distinct masses, some- 

 what in the manner seen in the commencement of ordinary cell division. As 

 there is no distinct nucleus, of course there are no precedent nuclear changes. 

 The masses thus formed gradually assume a more or less perfectly globular shape 

 inside the cell, although I have never been able to see that they there develop cilia, 

 and finally are set free by the lifting up of the end of the mother-cell, like a little 

 trap-door. Their mode of escape through the exit thus ofi'ered is similar to that 

 of the ordinary zoospore, which they resemble, except that they are much smaller, 

 are much less rich in chlorophyl, and have the anterior clear space less defined. 

 They are said to be furnished with a crown of cilia similar to that of the zoospore. 

 I myself have never seen these, but do not doubt their existence. 



In the dicecious CEdogonia there are distinct filaments, male and female, one of 

 which produces the oosporangium with its contained germ, whilst the other gives 

 rise directly to the spermatozoids. 



The resting spore which develops after impregnation is variously shaped, but in 

 most instances is round or oval. It is often, if not always, furnished with two coats, 

 the outer of which is thick, firm, and frequently provided with surface appendages, 

 such as tubercles, ridges, spines, etc. Besides these there is also, probably, a very 

 delicate inner coat. The spore appears to be set free from its case by the decay of the 

 latter, there being never, at least that I have seen, any regular dehiscence. Although 

 I have made several attempts, it has never been my good fortune to observe anything 

 like germination of these resting spores. Prof. Chr. Vaupell, however, has published 

 an account of the manner as observed by himself. Some water containing fruitful 



