Fritsch. — The Moisture Relations of Terrestrial Algae . /. 7 
Material kept in a constantly saturated atmosphere exhibits an 
increase in weight above that normally observed in the open air, and, 
conversely, material placed in a desiccator over calcium chloride exhibits 
a greater decrease in weight than is to be observed in the open. In either 
case, however, an approximately constant value is reached after some days. 
If such material is subsequently left exposed to the air, it exhibits a decrease 
and increase in weight respectively till that normal (or the hygrometric 
state of the atmosphere is attained. 
I 11 relation to the absorption of atmospheric moisture by various fabrics, 
Trouton and Pool (1906), as well as Masson and Richards (1906), have 
SEPT 1 6^ S £ PT 1 7*5 SEPT' 8 th “ SEPT r 9® 
Fig. i. Comparison of charge in moisture-content of the srme area of powdered soil and 
Fleurococcus naegelii in relation to atmospheric humidity. The hygrograph record for the period 
Sept. 6-9, 1919, is reproduced at the top, the graphs ol moisture-content of soil (continuous line) and 
alga (interrupted line) below. Noon of each day is indicated by a heavier line. 
independently established that (in the words of the former) * the weight of 
water absorbed or held by a given material under different conditions of 
moisture and temperature of the atmosphere appeared to depend only on 
the hygrometric state (i. e. the ratio of actual vapour pressure to the 
maximum possible), though of course the actual amount of moisture 
present in the atmosphere for the same ratio is very different at different 
temperatures’ (loc. cit., p. 292 ). In my experiments the materials used 
were scarcely ever allowed to attain an equilibrium value, and consequently 
I am at present unable to say whether this statement holds true for the 
algae investigated. If it obtained, the range (over a period of several 
