HOW TO KNOW THE SEAWEEDS 



78a Thallas perforated, net-like. Fig. 113 HydToclathrus clathratus 



Fig. 113. Hydroclathius clathra- 

 tus (Bory) Howe 



A small portion of a reticulate 

 plant, X 1.5. This is a species 

 of wide tropical distribution 

 which may be encountered in 

 our area along the Florida coast 

 and occasionally in southern- 

 most California. 



Figure 1 1 3 



78b Thallus crustose, not perforated, not net-like 



79 



79a Thallus reddish to purplish when wet 



80 



79b Thallus dark brownish in color when wet, at least not reddish or 

 purplish 81 



80a Thallus firmly adherent, composed of very small, cuboidal cells; 

 tetrasporangia irregularly zonate, borne in cavities. Fig. 114.... 

 Hildenbrandia prototypus Nardo 



Fig. 114. Hildenbrandia prototypus Nardo 



A vertical section through a tetraspor- 

 angial conceptacle showing the arrange- 

 ment of the sporangia and the small, 

 cuboidal vegetative cells, X 150. Com- 

 mon along both coasts as a .red film on 

 intertidal rocks and on shells. 



Note the absence of rhizoids from the 

 basal cell layer in comparing with Pey- 

 ssonelia below. 



Figure 1 14 



88 



