EUPHYCOPHYTA I03 



It has also been shown that the form of the thallus in some of the 

 species is largely dependent upon the conditions of the habitat, a 

 feature particularly well illustrated by the plastic C. cupressoides 

 and C. racemosa : 



(i) In exposed situations the plants are small and stoutly 



built. 

 (ii) In more sheltered habitats the shoots are longer and more 



branched, 

 (iii) In deep water the plants are very large with richly branched 

 flabellate shoots. 



Fig. 58 Caulerpa. A, B, C. prolifera ( x \). C, C. racemosa f. 

 macrophysa ( x \). D, E, C. sertularioides, side branches ( x ^). F, 

 C. crassifolia f. mexicana ( x i). G, structure of wall and two skeletal 

 strands. H, longitudinal section of aerial portion showing longi- 

 tudinal (/) and transverse (f) support strands. I, transverse section of 

 rhizome with skeletal strands. J, K, L, C. prolifera^ reproductive 

 papiUae ( x 5). M, C. prolifera with gametes being Uberated. 

 (A-Fj after Taylor i G-I, after Fritsch; J-M, after Dostal.) 



There is no septation, but the coenocyte is traversed instead by 

 numerous cyUndrical skeletal strands, or trabeculae, arranged per- 

 pendicularly to the surface and which are most highly developed in 

 the rhizomes. They arise from rows of structures termed micro- 

 somes, and are at first either free in the interior of the coenocyte or 

 else connected with the wall, although in the adult state they are 

 always fused to the walls. The function of the trabeculae, which 

 increase in thickness at the same time as the walls by successive 

 deposition of callose, is extremely problematical and may be : 



