HOW TO KNOW THE SEAWEEDS 



I39a Thallus pinnately branched only from the primary axis, the blades 

 being simple 140 



139b Thallus with several orders of branches 141 



140a Lateral blades smaller and shorter than terminal blade and usu- 

 ally of different shape. Fig. 179 Alalia 



Fig. 179. Alaria marginata Postals & Ru- 

 precht 



An entire small plant with some of the 

 lower pinnate blades (sporophylls) re- 

 moved, X 0.12. This species of northern 

 California and southern Oregon is one of 

 several kinds which occur in the colder 

 waters of both coasts. The alarias reach 

 their richest development along the Alaska 

 Coast, but four species occur from central 

 California northward and five others on 

 the Atlantic shores of northern Massachu- 

 setts and Maine. An Alaskan species, A. 

 fistulosa is one of our most massive giant 

 kelps, reaching lengths of more than 75 

 feet. 



Figure 179 



137 



