460 Fresh-Water Algae, of Canada. 



nor conjugation of cells? That such species are permanent, 

 and germinate from spores or zoospores produced in the cells, 

 we . entertain no doubt, or at all events, from the evidence 

 before us, we regard it as highly probable. It is possible that 

 future and more careful research may yield a different result. 

 In the meantime, aDd with all humility, we propound these 

 views. They are contrary, we know, to the inductions of 

 naturalists of the highest distinction and most accurate obser- 

 vation ; but we submit them to our botanical friends in the 

 hope that they may lead to enquiry and the elucidation of the 

 truth. Our intelligent correspondent in Paris informs us that the 

 research of the past year has failed to discover any but one single in- 

 stance of conj ligation (fig. 6). There must therefore, we think, be either 

 a specific difference between our plants and the European, or the 

 characters referred to must not be essential to the reproduction 

 of the species. In the absence of conjugation we have found a 

 difficulty in fixing npon characters that may be regarded as specific, 

 The length of the cells and the number of spiral threads fre- 

 quently vary in the same filaments. Still it does appear that 

 there is a normal size of the cells, and a normal number of spiral 

 threads and coils in the several species, which may* after a little 

 experience, be readily distinguished ; other forms are obviously 

 exceptional. The cells grow by sub-division, previous to which 

 they are somewhat elongated, and afterwards considerably short- 

 ened, until they attain maturity. The normal length will conse- 

 quently be that which lies between the two extremes. The same 

 process of growth will naturally somewhat affect the spiral threads 

 also, and produce anomalies in their form during their state of 

 transition. So far, therefore, we know of no characters by which 

 to determine our Canadian species except the size of the cells, the 

 number of their spiral threads, and other normal arrangements of 

 the endochrome. 



Genus Zygnema. Ag. 



" Char. — Endochrome arranged in spiral order within each cell. 



Sporangia generally oval, and never lodged in the transverse 



tabes of communication." Ilass. 

 Derivation. — zugos, a yoke ; nema, a thread. 



Hassall, Brit. F. W. Alg. ; Vauch. Conf. d'Eau douce; Bory 

 in Diet. Class. 



This genus is placed first in order in the family as being the 

 most remarkable in its appearance and complicated in its structure. 



