1 62 



MORPHOLOGY. 



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, Ijut 

 the protoplasm in each cell usuall}' divides into sixteen small cells, and 

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

 size (fig. i66). 



341, The Conjugatese include several families of green algte, which prob- 

 ably should he included among the Chlorophyceie. They have probably 

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

 coideae. They are represented bv Spirogyra, Zygnema, and the desmidS; 

 studied in Chapter 14. 



342. Subclass CONFERVOIDEJE.— These are mostly filamentous algse, the 

 filaments being composed of cells firmlv united, and, Avith the exception of 

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

 are as follows: 



-These contain 



343. Family TJlvaceae. 



Fig. 107. 

 Ulothrix zonata. .4, base of thread. B. 

 cells with zoospores, C, one cell with zoospores 

 escaping another cell \\'ith small biciliate 



gametes escaping and some fusing t':) form i 1 z^i i 



zygospores. £. zoospores germinatmg and represented by Lhietophora Un 



the sea w'racks, or sea lettuce, 

 like Ulva, forming expanded 

 green, riljbon-like growths in the 

 sea. 



344. Family TJlotrichaceas, 

 repre->rnk'd l.iy Uiothrix /.onata, 

 not UHLummon in slow-running 

 water or in ])onds of freshwater 

 attached to rocks or wood. It 

 consi.sts of simple tlireads of 

 shtjrt (.ells. I\Iulti]}hcati(.'n takes 

 place b)' zoospores. Repro- 

 ductifjn takes place by motile 

 sexual cells (gametes) which 

 fuse to form a z}'gospore (fig. 



345. Family Chsetophoraceae, 



forming threads F, f'7, zygospore growing and ri-nTifpr t"^ .snd Drinprmndi'i 

 ■■ ■ erCaldwell and Dodcl- ^'^'^l'^*^^ ^:>^ ^'^^ i^rapernauoia 

 Port.) in fresli water. 



forming zoospores. (After 



346. Family CE logoniaceas, rc]jresented by (Edogonium (Chapter 16). 



347. Family Coleochgetaceae, re[)resented by Coleocha'te (Chapter 17). 



348. Subclass SIPHONEJE.— There are several famihes. 



349. Family Botrydiaceae.^l'his is represented by Potn-diuni granu- 

 latum (Chapter 15, p. i4f>). 



360. Family Vaucheriaceae, re])resenled by \\iucheria (Chapter 15), with 

 quite a large number of species, is widt-ly distributed. 



