PHYSIOLOGY AND MORPHOLOGY OF CALIFORNIA HEPATIC 13 
In his studies upon Lophocolea bidentata, Cavers* found that 
the tissues of the gametophyte are entirely free from hyphe, 
but the rhizoids which grow out in tufts from the bases of the 
amphigastria penetrate the substratum of rotten wood and there 
become profusely branched like the haustoria of many fungi. 
This, he considers, enables the liverwort to assume a more or 
less saprophytic existence. He has not however shown that the 
plant actually does adapt itself to this mode of life, nor does it 
appear that we can assume the branching of the rhizoids as due 
to anything other than contact stimulus. Peirce and Randolph” 
have demonstrated that in the case of certain attached fresh- 
water alge and in many marine forms the development of a 
holdfast is directly and wholly the result of contact stimulus. 
The complexity and extent of the holdfast were found to vary 
with the degree of roughness of the surface of the substratum ; 
young plants grown on ground glass developing much more 
elaborate holdfasts than similar plants grown on smooth glass 
while those grown in dust-free water developed no holdfasts at all. 
In Knop’s solution the writer now has plants of /ossombronza, 
Cryptomitrzum and other liverworts growing that were removed 
from a normal soil substratum some months ago. Still attached 
to these plants are some of the old rhizoids which are all more 
or less gnarled and modified, some exhibiting short lateral proc- 
esses. Since placing the plants in Knop’s solution a great 
number of rhizoids have developed and in every,*7stance they 
are perfectly straight and unmodified and much more delicate 
in structure than those that had grown while the plants were in 
their normal habitat. We have here exactly the same behavior 
exhibited by the secondary roots and root-hairs of higher plants. 
If, as some botanists maintain, the rhizoids of bryophytes are 
simply organs of attachment is it not probable that, as in the 
case of certain algz, these branches are due to the stimulus 
afforded by contact? 
Aside from Aneura and Fossombronza the writer has observed 
branching rhizoids in Cephalozta bicuspidata, due probably to 
BICOC.“Gite,(p.. 32: . 
*Peirce and Randolph, 1905: Studies of Irritability in Algz. Botanical 
Gazette, 40° pp. 321-350. 
