ConfervecB?^ zygnema. 359 



ZYGNEMA, Agardh. 



Gen. Char. Pilaments articulated, simple, finally united in 

 pairs by numerous transverse tubes. Endocbrome consisting of 

 granules arranged in spiral rings, or in a simple row, which, after 

 conjugation, are condensed into a globule in one of the filaments, 

 or in the transverse tubes. — The name is from the Greek words 

 signifying a yoke and a thready the threads, though at first se- 

 parate, being afterwards yoked together. — Harvey. 



Zygnema is one of the genera of tlie order Conjugates, 

 The Conjugatem are undoubtedly tlie most curious tribe 

 of Confervm. Their filaments are simple^ and of uniform 

 diameter. They are mostly unattached, and, being the 

 inhabitants of stagnant waters, are in no danger of being 

 disturbed in their curious process of fructification. The 

 simple filaments are composed of elongated cells, placed end 

 to end, and held together by an enveloping membrane. The 

 interior of these cells is occupied chiefly with endochrome, 

 sometimes like stars, spirally arranged, and at other times 

 filling the cavity of the cells. What follows is very remarkable. 



When the filaments are fully grown, as they are in close 

 juxtaposition to each other, the cells are observed to send 

 forth little conical processes or tubes, which unite with 

 similar protrusions from corresponding cells of an adjoining 

 filament, thus establishing a passage of communication 



