F. Borgesen: Rhodophyceæ of the Danish W. Indies. 



283 



the cells is about 12// long; they have rather thick walls. Upon 

 the branchlets the trichoblasts are much smaller, the filaments 

 above the forking consisting of a single cell only. In his plant 

 Falkenberg did not find more than two to three cells in the 

 filaments of the trichoblasts. 



From the basal segment of each trichoblast a branch is devel- 

 oped. As is pointed out by Falkenberg this is placed quite, or 

 very nearly in 

 themanner of an 

 axillary branch. 

 These axillary 

 branches in- 

 crease very 

 quickly and as- 

 sume at an ear- 

 ly stage the car- 

 tilaginous consi- 

 stency of the 

 whole thallus. 



When young 

 they are inward- 

 ly bent, shelter- 

 ing the summit 

 of the plant. The 

 trichoblasts are 

 shed early and 

 leave no scars, 

 their place being 



quite effaced by the cortical layer which is most abundantly de- 

 veloped just at the base of the branches. Most of these branches, 

 after having reached a certain length, stop their development and 

 become the spiny branchlets characteristic of this species (Fig, 

 283). Now and then one of these branchlets assumes continuous 

 growth and grows out like the main filaments. 



The ramification of the branchlets takes place quite in the 

 same manner with the exception only that, as mentioned above, 

 the growth is soon stopped. 



My material contained sterile plants only. 



Bryothamnion triquetrum is fairly common in shallow water 

 in sheltered as well as somewhat exposed places; sometimes it 

 grows in rather large societies. Further it is also dredged in 



Fig. 282. Bryothamnion triquetrum (Gmel.) Harv. 

 1—6, successive generations of branches and trichoblasts. 

 The cells in the basal part are brought somewhat in 

 disorder by the preparation and the branches and tricho- 

 blasts, also, are not quite in their exact place. (About 330:1). 



