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1903] CURRENT LITERATURE 237 
solutes as by any other part of the body. The support for this view is found 
in the fact that where anchoring organs are most needed there they are 
surface and texture of substratum. In epiphytic and rock species they are 
best developed; in streaming mosses they form a dense tuft with strongly 
thickened walls, probably variable according to speed of current; but 
floating species have no rhizoids. Paul questions the existence of saprophytic 
penetration is made possible by the pioneer activity of other organisms; and 
that the nutritive activity of the protonema and leaves is adequate. He 
finds no evidence that the rhizoids of rock species in any way attack or 
destroy the rocks by secretions. What disintegration they produce is by hold- 
ing water. He expressly disclaims denying absorption of water and solutes 
by rhizoids, but holds that this is only such (or even not so much) as other 
parts of the body do. No secretions by rhizoids dissolve the substratum. 
Rhizoids are therefore by no means equivalent physiologically to root hairs. 
