456 



Fresh-Water Algm of Canada* 



their young condition they are smooth and unctuous to the touch,, 

 and of a deep green color. " They are composed of an assemblage 

 of elongated cells placed end to end, and all of them enclosed and 



Fig. 



4. Zygnema varians, showing the spiral thread T the conjugation T andi' 

 the sporangia. Hass. Brit. F. W. ^lg. r pl. 29. 



held in union by an investing membrane. The interior of these- 

 cells are chiefly filled with endochrome, which is variously dis- 

 posed, sometimes in the form of spiral threads and stars, at others 

 completely filling their cavities." Mixed up with the endochrome 

 there are observed numerous vesicles, which are presumed to be 

 unfertilized zoospores. Sometimes adjacent cells conjugate, (fig. 

 6, a.) and their contents coalesce; and sometimes the conjuga- 

 tion takes place with a cell of a contiguous filament, (figs. 4 and 6> 

 S, p. 459) a passage of communication having been formed by the 

 protrusion of little tubular processes from each cell. This phe- 

 nomenon of conjugation is one of the chief characteristics of this 

 large family of plants,, and it is certainly a very curious process^ 

 The idea of most botanists is that it is necessary in order to- 

 the fecundity of the plant — that fertilization does not take place 

 — sporangia are not formed — until this process has been com- 

 pleted. There is however no regularity in the passing of the con- 

 tents of the cells of one filament into that of the other, neither is 

 there anything analogous to the pistils and stamens of flowering 

 plants; nor does it appear that the one plant is male and the 

 other female, or that there is any difference in the physical cha- 

 racter of the granules contained in either cell. The larger celb 



