66 Rhodora [Marcu 
December 21, 9.30 A. M., il weighed .337 gram. 
December. 22, 4.45 P.-M., it weighed .230 gram. 
December 28, the weight had not apparently changed. 
Dry weight, .195. Humidity during test, about .93. 
Thus in 31 hours the percentage of water fell from .42 to .15, when 
equilibrium was reached. 
Sphagnum, sp. The material was picked from a recently collected 
but pretty dry heap of the moss, and the dead portions removed, leav- 
ing tips perhaps two inches long. One lot was weighed as it came 
from the shed — wt. .810 gram— and put into the box. In one day 
the weight fell to .555 gram. ‘Then being dried out to .495 gram, and 
again subjected to the action of the moisture, the sphagnum increased 
its weight to .530 gram in six days, and .540 gram after a further ex- 
posure. Dry weight, .420 gram. 
The second lot was kept in the laboratory for two days, when it 
seemed utterly dry to the touch, but was still alive and green. Weight, 
.620 gram. Seven days later it weighed .630 gram. Dry weight, .500 
gram. 
In both cases there was some intake of water-vapor. In one the 
percentage of water rose to .20, in the other to .22. At best the moss 
remained in a state of relative desiccation. 
It was hard to believe that the power of vapor-absorption detected 
could be of any practical importance in the economy of the plant, at 
least under the natural conditions prevailing in this part of the world. 
This conclusion is confirmed by the following observation. Both 
Sphagnum and Leucobryum, killed and dried at 100^ C. and then re- 
placed in the moistening chamber, rapidly took up vapor. In less than 
24 hours the water contents of the dead moss thus derived, equalled 
that left when the living plants were allowed to dry out for one or two 
days in the same receptacle. 
LicHENs. As compared with the other plants experimented upon, 
lichens show a considerable power of condensing atmospheric mois- 
ture. But though the absorption is enough to render lichens that come 
from outdoors in a harsh and brittle condition soft and flexible after a 
day or so, the highest proportion of water obtained by imbibition of 
vapor is very far below that which the lichens hold when well saturated 
by dew, rain, or soil-water. 
The following figures will serve for illustration. Usnea barbata is 
the common much-branched lichen growing in tufts on the twigs and 
