242 



no indications as to the position of the tetrasporangia; J. AGARDH 

 gives a very good and detailed description of it. Judging from that 

 this species appears to be like a Ceramium diaphanum, regularly 

 dichotomous and with isolated projecting tetrasporangia. However, 

 when these organs are not present, this species is not easily 

 recognizable. 



In referring the present specimens to Ceramium fastigiatiim we 

 have in view the shape and size of the tetrasporangia. As these, how- 

 ever, do not seem to agree en- 

 tirely with the typical form de- 

 scribed by HARVEY (Phyco- 

 logia Britannica, pi. 255) it 

 seems preferable to con- 

 sider them as representing a 

 special form: f. flaccida, so cal- 

 led because their filaments are 

 extremely thin and flabby. 



The tufts are 4 5 cm 

 high, built up by dichoto- 

 mous threads. The axial cells 

 are about 400 n long, 50 // 

 broad, with zones 30 40^ 

 high and 50 fj. broad, often 

 only 20 // high. The zones do 

 not increase in the margins; 

 the upper marginal cells are 

 often smaller than the other 

 cortical cells. No glandular 

 cells are present. The sum- 

 mits of the filaments are not 

 very curved and the zones 

 are here quite close together. The tetrasporangia are isolated and 

 prominent. Sexual organs are not present. 



Of the specimens of C. fastigiatu?n distributed in Phycotheca 

 Bor.-Am., No. 446 the uppermost one of those belonging to the 

 Botanical Museum, Copenhagen, agrees in some respects with the 

 present form, especially as to the shape and size of the zones. 

 The other specimen is a typical Ceramium stnctum. 



Ceramium jastigiatum L flaccida is found in sheltered locali- 

 ties and in shallow water and grows upon the roots of the man- 

 groves, to which it is fastened by means of mostly short, uni- 



Fig. 231. Ceramium fastigiatum (Roth) 

 Harv. f. flaccida H. E. P. a, part of a 

 young filament; b, part of an older one; 

 c, zone with tetrasporangia. (About 

 250:1). H. E. P. del. 



