HOW TO KNOW THE SEAWEEDS 



74a Branching opposite, at least in major part. Fig. 1Q7. . Antithamnion 



Figure 107 



Fig, 107. Antithamnion sp, 



A small upper part of a fertile plant showing the opposite 

 branching and the position of tetrasporangia, X 80. This is a large 

 genus of very delicate, beautiful plants which are commonly epi- 

 phytic. Some species are quite small, while others reach 20 cm. in 

 height. They may be encountered on any part of our coasts and 

 must be identified specifically through the use of the various local 

 floras. 



74b Branching alternate, dichotomous or irregular (sometimes partly 

 or wholly opposite in Spermothamnion turneri) 75 



83 



