Chsetophorese 



295 



Microthamniese are mostly reduced forms resulting from the adoption of an 



epiphytic or endophytic mode of life. 



The irregular character of the thallus 



in the Gomontieae is also the result of 



specialization. 



Sub-family CHSETOPHORESE. In this 

 sub-family are included all the best 

 developed types of the Chsetophoracea?, 

 in which, as a rule, the main portion 

 of the thallus consists of free erect 

 branches, much attenuated and often 

 piliferous (Ch&tophora, Draparnaldia, 

 etc.). The basal attachment, which 

 consists of recumbent and more or less 

 concrescent branches, is usually small 

 and rather insignificant, but in Bulbo- 

 coleon, Pseudochtete and Endodonium 

 it is of more importance, and in Tricho- 

 discus it is the most conspicuous part 

 of the thallus. 



In some of the genera, more 

 especially Chxtophora and Drapar- 

 naldia, the thallus is enveloped in 

 copious mucilage, which in the first- 

 named genus is so firm and tough that 

 the thallus as a whole possesses a 

 definite external form (consult fig. 

 188 A and C). A few of the Chasto- 

 phoreaB are encrusted with lime, 

 notably Fridtea torrenticola Schmidle and several forms of Chxtophora, 

 (Ch. incrassata var. crystallophora Ku'tz., Ch. calcarea Tilden, '97, etc.). 

 Draparnaldia is unique among the Chastophorese in the possession of a main 

 filament of large cells forming a little-branched axis which bears numerous 

 tufts of small branchlets (fig. 190 A). In the axial cells the chloroplast is 

 frequently perforated, and in D. platyzonata is truly reticulated (fig. 190 B). 

 Perforated chloroplasts also occur in Bulbocoleon and sometimes in Chtetonema. 



In the epiphytic genus Tkamniochsete (fig. 191 C) the thallus has been 

 reduced to very few cells, one or two of which bear long, tubular or solid 

 hairs. This greatly reduced thallus represents the erect portion and there is 

 no attempt at the formation of recumbent branches. Two other reduced 

 forms, also epiphytic, are Bulbocoleon (fig. 191 .4) and Acrochtete (fig. 191 B}, 



Fig. 189. Stigeoclonium tenue Ag. A, part 

 of thallus, x 100 ; B, escape of macro- 

 zoogonidia ; C, escape of microzoogonidia 

 (or gametes?) ; D and E, macrozoogonidia ; 

 F, conjugation of gametes to form zygo- 

 spore ; G, germination of a cluster of 

 zoogonidia. B G, x 500. 



