HOW TO KNOW THE SEAWEEDS 



53b Plants reddish, with a midrib 54 



54a Thallus simple, without macroscopic lateral veins. Fig. 84 



Grinnellia aznericana 



Fig. 84. Grinnellia americana (C. Agardh) 

 Harvey 



A single blade of an asexual plant to 

 show the simple, ruffled character, ab- 

 sence of lateral veins from the midrib, 

 and the small tetrasporangial sori, X 0.8. 

 This is an attractive plant of pleasing color 

 and form which is sure, to appear in sum- 

 mer collections from our north central At- 

 lantic Coast. It inhabits warm quiet water 

 in wading depths at low tide, maturing and 

 disappearing by late summer. It may be 

 encountered from South Carolina to as far 

 north as northern Massachusetts. 



Figure 84 



54b Thallus pinnately lobed; midrib with distinct, opposite lateral veins. 

 Fig. 85 Phycodrys 



Fig. 85. Phycodrys rubens (Hudson) 

 Batters 



A single blade to show lobing and 

 veination, X 1. This is the only spe- 

 cies of the genus on the Atlantic Coast, 

 occurring from New lersey northward, 

 especially north of Cape Cod. The 

 common Pacific species is P. setchellii 

 found in California and Oregon. 



Figure 85 



69 



