Dasycladese 



269 



Sub-family DASYCLADE^E. In the members of this sub-family the thallus 

 is not at all, or only slightly, encrusted with lime. The main axis bears 

 numerous lateral branches, dichotomously or polytomously arranged. All 

 the terminal or lateral segments may be fertile. 



In Dasycladus (fig. 172) the axial coenocyte is clothed with whorls of 

 branches, about twelve to each whorl. These branch-segments are again 

 branched several times, the size of the segments diminishing with each 

 successive branching. There is a slight calcification of the outer part of the 

 wall of the axial coenocyte (consult fig. 172 3 and 4- &) In a fertile plant 



172. Dasycladus clavfeformis (Both.) Ag. 1 and 2, general habit of sterile and fertile 

 plants, about nat. size. 3, part of a whorl of branches, x about 40 ; stz, ' stem-cell ' ; 

 w, w", w'", whorl-branches of different orders; c/, gametangiurn. 4, transverse section 

 through the wall of the ' stem-cell ' ; m, inner cellulose part of wall ; k, outer calcareous 

 part ; iv', basal parts of branches of first order ; t, minute canal. 5 S, gametes and fusion 

 of same. (4, after Nageli, others after Oltmanns.) 



a spherical, shortly stalked gametangium may be developed on the end of 

 each of the basal branch-segments (fig. 172 3 g}, especially on the upper 

 part of the thallus (fig. 172 #). The gametes are isogamous and fuse in 

 pairs (fig. 172 5 8) to form zygotes, but the germination of the latter has 

 not yet been observed. 



In Chlorocladus, a genus in which the terminal segments of the apical 

 branches are piliferous, the fertile branches produce ' aplanosporangia ' with 

 numerous ' aplanospores,' the further development of which is unknown, 

 although it is suspected that they ultimately become gametangia. In 

 Batophora the general habit is of a simpler type and only ' aplanospores ' are 

 formed. 



