28 
inward and upon themselves until they are so ihe curled that 
but little moisture can evaporate ; they unroll rapi when moist- 
ned, and are thus iaeees ee nied to avail ae of 
and gain time, 
ee favorable change of itions, 
this way, on their less sdapiable companions. 
Most mosses absorb aqueous vapor from the air very rapidly 
have leaves especially adapted for this purpose ; those 
which bear gills on their upper surfaces, arranged as if they were in- 
m into channels lead- 
into hollows at the base of the 1 
ceed for some time after the remainder of the leaf is d 
devices occur in the leaves of the hair-cap mosses (Polytrichums), 
the Catharineas, and h rded mosses (Barbula), 
One species of pane ws ae growing in the Hemlock 
Grove has been made th n experiment in which 
specimens taken from a e rock 
of its ee in water. 
The various peat mosses are furnished with leaves containing 
large air ie or cavities with small openings, 4 such plants 
re able to take up many times their own weight or bulk o! 
The absorbent power of these mosses ins led to their 
use as oe in pues = ame ae are crushed and the air- 
aviti ost. This was demon- 
strated when a s cashich of white moss ne glaucum) was 
subjected to hydraulic pressure. Although afterward immersed 
ion 
uring the winter months many of the mosses keep on their 
hoods to protect the green and growing aN box, and most of 
them retain this covering until spring. Thi nin ive 
species recently observed in the Garden : a tharinea angusta 
Tortula muralis, the little green Weisia, Dicranella het sas 
with its numerous cylindrical spore cases, and Zvi pee 
The hood or calyptra of the last named species usually falls off 
very early however. 
