458 



Fresh-Water Algoe of Canada. 



been noticed by Mr. Bowerbank in a species of Zygnema, which 

 I transmitted to him, and subsequently by myself in a variety of 

 other species. The one is cruciform, and adherent to the inner 

 wall of the cell, (see Fig. 5). It, Mr. Bowerbank remarks, is the 

 vegetable structure which secretes the raphides. They are pro- 

 bably not definite organs, but crystals. The other body is small, 

 elongated, somewhat curved, and attached to or lying upon the 

 plant, (see Fig. 5). This, Mr. B. observes, is certainly a string of 

 minute cytoblasts." — Hass. 



Fig. 5. Cell of Z. nitidum, showing the spiral threads containing spores 

 the cyloblast, and the cruciform raphides. Hass. F. W. Alga, plate 17. 



We have collected and examined with great care multitudes 

 of these plants — they are to be found in great abundance in almost 

 every stagnant pool — and only in oue instance (Z. curvatum) have 

 we, during a period of two years, observed conjugation in the 

 L. Canadian specimens. "We eagerly looked for it last spring, the 

 time of the year, at which, according to Hassall, it is most usu- 

 ally found in England, and have, up to the beginning of winter, 

 almost every week examined specimens from various localities, 

 and in all conditions of growth, but in no instance have we 

 found conjugation, with the exception noted. We have also failed 

 to discover in any case the cytoblastic organ. 



A specimen has however been sent us of Z. catenceforme from 

 Paris, C. W., about 360 miles S. West from Montreal, which 

 curiously presents the three forms in which conjugation is some- 

 times found. In the following figure (6) it will be seen that at 

 (a) the contiguous cells are in conjugation, while at (b) it is the 

 contiguous filaments, and that the contents of the opposite cells 

 pass alterately into each other. 



From these considerations one would be led to infer that these 

 characters are either very evanescent in their nature and rapid in 

 their functions, or that they are mere accidental conditions of 



