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 Conjugatese include several families of green algae, 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- 

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

 studied in Chapter 14. 



342. Subclass CONFERVOIDEJE. 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 Ulvaceae. These contain the sea wracks, or sea lettuce, 



like Ulva, forming expanded 

 green, ribbon-like growths in the 

 sea. 



344. Family Ulotrichacese, 

 represented by Ulothrix sonata, 

 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 



Fig. 167. fuse to form a zygospore (fig. 



Ulothrix zonata. A, base of thread. B, j^") 



cells with zoospores , C ', one cell with zoospores ' ' ' 



escaping another cell with small biciliate 345. Family Cnaetophoraceae. 



gametes escaping and some fusing to form , , .^, , ,. 



zygospores, E. zoospores germinating and represented by Chaetophora (in 



forming threads F, G, zygospore growing and Cbxntrr TC^ and Dranernanrlin 



forming zoospores. (After Caldwell and Dodel- Cna P te 



Port.) in fresh water. 



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



347. Family Coleochaetaceae, represented by Coleochaete (Chapter 17). 



348. Subclass SIPHONE2E. There are several families. 



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

 latum (Chapter 15, p. 146). 



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

 quite a large number of species, is widely distributed. 



