HOW TO KNOW THE SEAWEEDS 



122b Terminal tuft consisting of filaments which are united, at least in 

 part, into small blades. Fig. 161 Rhipocephalus 



Fig. 161. Rhipocephalus phoenix (So- 

 lander) Kiitzing 



An entire plant, X 1.2. 



There are only two species of 

 this interesting genus which is con- 

 fined to the West Indian region. Both 

 of them occur in southern Florida in 

 the same kinds of sandy habitats oc- 

 cupied by Penicillus and Udotea. R. 

 phoenix is the more abundant and 

 widespread of the two, and it is for 

 its recognition that the union of the 

 filaments of the terminal tuft into 

 small, narrow, flabellate blades is 

 pointed out in the key. In the other 

 species, R. oblongus, these filaments 

 are united only in youth, and older, 

 well developed specimens may rather 

 closely resemble Penicillus capitatus. 

 Inasmuch as all of these plants may 

 be found growing together, one 

 should attempt to make series of 

 specimens of all sizes and ages in 

 order, by comparison, to distinguish 

 them clearly. One will note that 

 small plants of R. oblongatus often 

 have funnel-shaped or markedly 

 elongate heads. Also, if one looks 

 closely for specimens showing the 

 partial or evanescent union of the 

 filaments of the head, he will have 

 found the distinguishing character of 

 the genus Rhipocephalus. 



Figure 161 



123 



