72 The Plant World. 



with the eastern more virescent examples, this being due, as 

 cross sections of the thallus prove, to a thicker cortex, obscuring 

 the consequently deeper buried algal layer. 



The reason for the luxuriance (not of length alone) of 

 Bavarian highland Usneas, particularly Usnea longissima, is 

 also, I think, to be explained by the large rainfall of the region,t.e. 

 60 inches per annum, and not a little no doubt to the frequence 

 of cloudy, damp days. The luxuriance of Usneas in equatorial 

 regions of South America and Africa is in accordance with the 

 larger rainfall, and this is particularly well shown in a compari- 

 son of plants from the eastern (wet) and western (dry) slopes 

 of the Andes in Bolivia. 



The Usneas reach as I have already said, their greatest 

 development in North America on the Coast ranges of the Pacific 

 coast, from Monterey county, California, to British Columbia, 

 especially on this coast between San Francisco and Chehalis 

 county, Washington, which area lies in the greatest rainfall belt 

 on the continent, and Mr. Herre in his prefatory remarks on 

 "The Foliaceous and Fruticose Lichens of the Santa Cruz 

 Peninsula" writes "The Pacific side of the peninsula is very 

 moist and in the fog-laden air of the redwood or forest formation 

 certain forms ot lichens reach a development perhaps unsurpassed 

 elsewhere." Have I said more than this? 



