1 62 



MORPHOLOG Y. 



dividing into thousands of minute cells, which gradually arrange themselves 

 in the form of a net, escape together from the mother cell, and grow into a 

 large net. In Pediastrum multiplication takes place in a similar way, but 

 the protoplasm in each cell usually divides into sixteen small cells, and 

 escaping together from the mother cell arrange themselves and grow to full 

 size (fig. 1 66). 



341. The Conjugates include several families of green alga?, which prob- 

 ably should be included among the Chlorophyceae. They have probably 

 had their origin from some of the more simple members of the Protococ- 

 coideas. They are represented by Spirogyra, Zygnema, and the desmids, 

 studied in Chapter 14. 



342. Subclass CONFERVOlDEJE. These are mostly filamentous algae, the 

 filaments being composed of cells firmly united, and, with the exception of 

 the simplest forms, there is a definite growing point. A few of the families 

 are as follows: 



343. Family Ulvacese. These contain the sea wracks, or sea lettuce, 



like Ulva, forming expanded 

 green, ribbon-like growths in the 

 sea. 



344. Family Ulotrichacess, 

 represented by Ulothrix /.onata, 

 not uncommon in slow-running 

 water or in ponds of fresh water 

 attached to rocks or wood. It 

 consists of simple threads of 

 short cells. Multiplication takes 

 place by zoospores. Repro- 

 duction takes place by motile 

 sexual cells (gametes) which 

 fuse to form a zygospore (fig. 



Fig. 167. 



Ulothrix zonata. A, base of thread. B, 

 cells with zoospores , C ', one cell with zoospores 

 escaping, another cell with small biciliate 



345. Family Chaetophoraceffi, 

 represented by Ouctophoia (in 



Port.) in fresh water. 



346. Family (Edogoniacese, represented by CEdogonium (Chapter 16). 



347. Family Coleochsetaceae, represented by Coleocha;te (Chapter 17). 



348. Subclass SIPHONEJE. There are several families. 



349. Family Botrydiaceae. This is represented by Botrydium granu- 

 latum (Chapter 15, p. 146). 



350. Family Vaucheriaceae, represented by Vaucheria (Chapter 15), with 

 quite a large number of species, is widely distributed. 



