229 



the large, subcylindrical tetrasporangia placed, as far as I have 

 seen, at the base of the filament. 



The plant has been found as an epiphyte upon old remains 

 of larger algae in shallow water and in a rather sheltered place. 



St. Thomas: In the harbour of this island near the town Charlotte 

 Amalie. 



2. Autithamnion spec. 



Having had only a few sterile, small specimens of this plant 

 at my disposal I prefer to let it remain without a specific name. 



The plant has 

 decumbent, creep- 

 ing filaments (Fig. 

 217), fastened to 



the substratum 

 (Sargassum vulgare) 

 by means of hap- 

 tera; these have a 

 short stalk consist- 

 ing of more or less 

 moniliform cells, 

 ending in a small 



irregularly lobed 

 disk. The cells in 

 the stalk are about 

 50^ long and 27 ij. 

 broad. 



The cells in the 

 creeping filaments 



Fig. 217. Autithamnion spec. Part of a decumbent 



filament with rhizoids and erect filaments 



(About 175:1). 



are nearly cylindrical with thick walls ; they are about 40 p broad 

 and 115 p. long. From these basal filaments the erect ones arise; 

 the ends of these creeping filaments often being assurgent too. 



The erect filaments are oppositely ramified, each joint bearing 

 two branchlets cruciately alternating with the pair below (Fig. 

 218). A few of these branchlets grow out as filaments like the 

 main stem ; by far the greater part remain short with definite 

 growth. The cells in the main stem are of variable size in the 

 different filaments; they are nearly cylindrical, a little thicker 

 above the place where the branchlets issue; their length varying 

 about 100 //, their breadth about 30^. 



The branchlets are alternatingly ramified. The lowest cells 

 in the branchlets are short often nearly spherical; the other cells 



