408 BOTANICAL GAZETTE | JUNE 
next raincomes. It may be dislodged again, for such fragments 
do not form even the small weak holdfasts developing on speci- 
mens which have grown from the spore (fig. p. 407). The 
dislodgement is, however, less common than one would at first 
imagine ; first, because of the ‘‘ double turn” which is so com- 
mon, and second, because the part thrown around the branch 
remains more or less fixed in shape, conforming to the branch 
somewhat as a tendril does to its support. That there is any- 
thing more than a mechanical reason for this I doubt, although 
there may be contact or chemical irritation at this point; tor 
even when thoroughly wet, the part of the lichen bent or coiled 
around a branch does not uncoil or become very loose. Whether 
this is simply the fixing of a certain form by the growth, com- 
pleted under mechanical stress, of the part of the lichen bent 
around the branch, or whether the growth is modified, directed, 
prolonged and finally terminated by the irritation set up by con- 
tact with the branch, I am not now able to say. Experiment 
only can settle this point, and experimentation with lichens is 
peculiarly difficult because of their slow growth. Against the 
idea that there may be irritation (contact or chemical), and a 
response thereto on the part of the hyphe, is the fact that these 
hyphz do not grow out from the lichen and attach themselves 
to the bark, there is no formation of anything like a new foot or 
holdfast such as the young lichen forms when growing from the 
spore. It is necessary, however, to consider the effect of con- 
tact with a branch not only upon the hyphe which touch it, but 
also upon the the gonidia and hyphz which may receive more or 
less nutritious solutions from the dead and decaying bark-cells. 
Observation leads to the belief that the fragment is simply 
caught by arough branch, twisted about this by the wind, and 
remains there indefinitely, or until, during some subsequent rain, 
it becomes detached, falls to the ground, or is blown away to 
another branch. 
The growth of any part of the lichen seems not 
impaired by detaching it from any other part. The fragments 
torn and carried away by the wind grow and fruit perfectly well; 
to be 
