ECOLOGICAL ADAPTATIONS OF CERTAIN FERN PROTHALLIA 479 
found in nature; to determine the effect of variation of light intensity 
upon development, and finally by checking up results from controlled 
cultures with findings in the field, to determine whether or not the 
peculiarities found are developed or of use in nature. 
Camptosorus rhizophyllus Link. 
As previously reported (Pickett, 1913, pp. 643-644), prothallia 
of this fern may survive an exposure of six weeks to air dried by passing 
through glycerine, but are killed by an exposure of four to six days 
over sulphuric acid in a closed desiccator. There are two possible 
explanations of this great variation, either the air is not entirely dried 
by the passage through the glycerine, or injurious gases are given off 
by the sulphuric acid. The work of Schroder and of Irmscher on 
mosses, as well as check experiments performed by the writer, seem 
to eliminate entirely the possibility of injurious gases being given off 
by the sulphuric acid. To determine the thoroughness of desiccation 
the former experiments have been repeated and new apparatus 
planned to furnish more thoroughly dried air. 
In the writer's earlier experiments, as a result of reduced pressure 
secured by means of an aspirator, a current of air was made to pass 
through two 20 cm. U-tubes containing glycerine and crumpled filter 
paper saturated with glycerine, and then through small vials containing 
the material to be desiccated. In this apparatus air bubbles of from 
2-3 cc. required 5-10 sec. in passing through the glycerine in the 
bottom of the tubes. The air was in further contact with the saturated 
filter paper about 15 min. In the experiments now to be described 
five methods of removing the moisture from the air have been em- 
ployed, designated I, II, III, IV, V. To secure pressure, positive or 
negative, for the production of a constant stream of air the apparatus 
shown in text-fig. i was used. Water from the tap allowed to flow 
through W into the funnel in a stream about 1/3 as large as the bore 
of the tube B (4 mm.) in passing intermittently through the reverse 
curve at B carries bubbles of air with it into the aspirator jar C 
The continuous stream of air and water passing into C tends to force 
the air through the tube V to E and thence through the other pieces 
of apparatus. Limiting the flow of air by means of screw cocks at / 
causes an increase of pressure in C until first the water and then the 
surplus air is forced out through D. The heights of tubes D and 
B determine the pressure available, and the number of tubes 
