204 



a few years ago, we have got a detailed description of this plant 

 to which I refer, restricting myself here to a short description 

 only and some figures of the West Indian plant, showing its 

 great likeness to and small differences from the North American 

 form. The chief difference is that the cells in the West Indian 

 plants generally are much thicker than those of the plants from 

 the North Atlantic. This applies especially to the cells in the 

 basal part of the thallus. In the West Indian form the cells are 

 nearly oval about 2mm. long and 1,3mm. broad, while in the 

 North Atlantic plant the cells are much thinner, but on the other 

 hand much longer, nearly cylindrical with somewhat swollen upper 

 ends. Higher up in the thallus of the West Indian plants the 

 cells are often nearly spherical, of very variable size, the larger 

 about 1,4 mm. broad. 



Compared to the sizes given by LEWIS, 1. c. p. 642, it is 

 evident that the cells of the West Indian form are larger and 

 also seem to have a somewhat different shape from the North 

 Atlantic one, but I do not think we can lay so very much stress 

 upon this fact, and Professor FARLOW has also most kindly in- 

 formed me that the shape and size of the North American plant 

 vary very much, especially in the tetrasporic and sterile specimens, 

 and as my plant, on the other hand, in its tetraspores, antheridia 

 and cystocarps, seems to agree completely with the description 

 of that from the United States I have referred it without any 

 doubt to this species. 



The West Indian plant forms dense, semiglobular tufts, 

 reaching a height of 6 cms. or more. It grows especially epiphyti- 

 cally upon calcareous algee, e. g. Halimeda, Penicillus etc., but is 

 also found upon stones and pieces of coral at the bottom of the 

 sea. The plant is fastened to the substratum by means of vigorous 

 rhizoids (Fig. 191 a) 1 ). These grow out from the basal cells, 

 having very thick walls and being very irregularly ramified. Also 

 from the basal end of the cells in the lowest part of the plant 

 rhizoids grow out, but they are shorter here and not ramified. 

 They grow downwards, attaching themselves to the upper end of 

 the cell below, contributing in this way to the strengthening of 

 the whole thallus (Fig. 191 a}. The wall of the cells in the basal 

 part are very thick and stratified. 



The thallus is repeatedly forked (Fig. 191 a) and, judging 

 from the young stages of division I have seen, the division 



l ) LEWIS, J. c. p. 653 points out that Griffithsia is anchored to the substra- 

 tum either by a special attaching disc, or by a tangled mass of rhizoids. 



