256 Siphonocladiales 



with many pyrenoids. Internal to the chloroplasts there are numerous and 

 very evenly distributed nuclei. Starch-grains are also present, but they are 

 more particularly accumulated in the rhizoids. 



Zoogonidia may arise in any of the branch-segments, the zoogonidangium 

 consisting of the original coenocyte of the mother-branch and the branch 

 grown out from it but not yet cut off by a wall. The zoogonidia escape through 

 several orifices which are slightly protuberant, and they germinate directly. 



Fig. 165. Struvea anastomosans (Harv. ) Piccone. a and &, extremities of young stalks showing 

 development of the ' frond.' c, more advanced stage, d, single plant isolated from a tuft, 

 showing the branched stalk with rhizoids. e, part of 'frond 1 showing how the branches 

 are mutually attached by means of tenacula. /, chromatophores with pyrenoids. a d, 

 x about 6 ; e, x 20 ; /, x 250 (after Borgesen). 



Most of the Siphonocladegs are tropical and subtropical ; they have a preference for 

 sheltered localities and moderately deep water, although they do occur in less abundance 

 in shallow water. Siphonocladus tropicus (Crouan) J. Ag. is often epiphytic on other 

 or, as in Ernodesmis verticillata (Kiitz.) Borges., it is not infrequently found in 



