HOW TO KNOW THE SEAWEEDS 



131a Thallus with a coarse, dichotomously branched stipe, but the 

 slender, ligulate blades simple. Fig. 171 . . . .Lessoniopsis littoTalis 



Figure 171 



Fig. 171. Lessoniopsis littoral- 

 is (Fallow & Setchell, ex Til- 

 den) Reinke 



The lower part of a young 

 plant showing the coarse, 

 forked stipe and Hgulate 

 blades, one of them intact, 

 X 0.52. Grows on rocks at 

 low tide level subject to heavy 

 surf, from central CaUfomia 

 northward. The ligulate blades 

 with midribs are always ster- 

 ile. Small fertile blades (spo- 

 rophylls) without midribs de- 

 velop year after year in lat- 

 eral pairs below the Ugulate 

 blades. This species and Pos- 

 telsia palmaefoTmis are among 

 the most striking of our Pa- 

 cific cumatophytes, or "surf- 

 loving plants" for there ap- 

 pears to be no limit to the 

 amount of wave shock they 

 can withstand. Lessoniopsis 

 grows at somewhat lower 

 levels than Postelsia, appar- 

 ently having less resistance 

 to desiccation which may oc- 

 casionally be prolonged dur- 

 ing calm weather coincident 

 with low tides. 



130 



