154 



MORPHOLOGY. 



and other plants, and has been found quite abundantly for sev- 

 eral years in the waters of Cayuga Lake at its southern extremity. 

 As will be seen it consists of a single layer of green cells which 

 radiate from the center in branched rows to the outside, the cells 

 lying so close together as to form a continuous plate. The plant 

 started its growth from a single cell at the central point, and grew 

 at the margin in all directions. Sometimes they are quite irregu- 

 lar in outline, when they lie quite closely side by side and inter- 

 fere with one another by pressure. If the surface is examined 

 carefully there will be found long hairs, the base of which is en- 

 closed in a narrow sheath. It is from this character that the 

 genus takes its name of coleochsete (sheathed hair). 



324. Fruiting stage of coleochsete. It is possible at some 

 seasons of the year to find rounded masses of cells situated near 

 the margin of this green disk. These have developed from a 

 fertilized egg which remained attached to the plant, and prob- 

 ably by this time the parent plant has lost its color. 



325. Zoospore stage. This mass of tissue does not develop 

 directly into the circular green disk, but each of the cells forms 

 a zoospore. Here then, as 



in cedogonium, we have an- 

 other stage of the plant in- 

 terpolated between the fer- 

 tilized egg and that stage 

 of the plant which bears the 

 gametes. But in coleochsete 

 we have a distinct advance in 

 this stage upon what is pres- Fig . IS7 . 



ent in cedogonium, for in . Portion of thallus of Co- 



leochaste scutata, showing 



coleochsete the fertilized em pty . ells . from which 



zoogonidia have escaped, 



egg develops first into a Pj: from f^Vl 11 ; Z ?,P~ 



t?< - 1 A nicliti at tlic IGtt. ^Alter 



several -celled mass of tissue Pringsheim.) 



Fig 158. 



Portion 01 thallus 

 of Coleochaete 

 scutata, showing 

 four antheridia 

 formed from one 

 thallus cell ; a sin- 

 ;le spermatozoidat 



e light. (After 

 Pringsheim.) 



f,! 



before the zoospores are formed, while in cedogonium only four 

 zoospores are formed directly from the egg. 



326. Asexual reproduction. In asexual reproduction any of the green 

 cells on the plant may form zoogonida. The contents of a cell round off and 



