HOW TO KNOW THE SEAWEEDS 

 141b Thallus reddish; growth not trichothallic 142 



142a Thallus provided with frequent small, hook-shaped branches; mid- 

 rib absent; microscopic veins present. Fig. 182 



Acrosorium uncinatum 



Fig. 182. AcTOSorium uncinatum (Turner) 

 KyHn 



Part of a plant bearing several of the 

 characteristic hooked branches, X 1.3. The 

 _,^y^ delicate veins, which must be seen with a 



lens, are not indicated in the figure. 



This is a common, epiphytic plant of 

 southern California. 



Figure 182 



142b Thallus without hook-shaped branches; midrib present, at least in 

 lower parts. Fig. 183 Nienburgia 



Fig. 183. Nienburgia andersoniana (J. Agardh) Ky- 

 Hn 



A small upper branch showing the midrib in 

 lower parts and the dentate margins of the blade, 

 X 1.2. Common at low intertidal levels, often in 

 grottos, under overhanging rocks, or under other 

 algae and surf-grass, from southern California to 

 Oregon. Another species, N. borealis Kylin, oc- 

 curs in Puget Sound. 



Figure 183 



140 



