ALG^ 



69 



The Conjugate 



The members of the second subsidiary order of the 

 green algse, the Conjugatae, are mostly fresh-water 

 plants, having very marked characteristics, and distin- 



FiG. 13 (Conjugatae). — A, two filaments of Spirogyra showing the he- 

 ginnlng of conjugation; each cell contains a single large spiral chlo- 

 roplast with the pyrenoids, p; B and C, later stages of conjugation; in 

 C the contents of one of the conjugating cells has passed completely 

 over into the other, the united protoplasmic masses forming the resting- 

 spore, sp ; D, Closterium, one of the Desmids or unicellular Conjugatae ; 

 p, a pyrenoid ; E, two views of another Desmid, Staurastrum ; the 

 shaded portion represents the chloroplast ; F, a Desmid, Cosmarium, 

 in process of cell-division. 



guished from most of the other algse by the complete 

 absence of ciliated cells. The most familiar members of 

 the group are the " pond-scums," which occur in large, 

 frothy masses, floating in quiet water. The lowest of 

 the order are the Desmids, perhaps the most beautiful 

 of all unicellular plants (Fig. 13). 



The lowest of the desmids are simple oval cells, with 



