PICKETT: RESISTANCE OF PROTHALLIA TO DESICCATION 645 
surface was dry at all times, except when occasionally flooded. 
The remaining portion was moist as in the other cultures. All 
gradations of moisture were in evidence in and between the two. 
regions. Small prothallia were seen on December 18 on the 
damp soil. On March 1, 1913, most of the prothallia of this 
region showed mature sex organs. The drier portions at the 
latter date showed germinating spores, dwarf male prothallia, 
and later stages in development up to mature plants. After 
March 1, this culture was watered irregularly and was allowed to. 
become quite dry each time before more water was applied. 
After April 15 the culture was screened from the direct sun. 
Water was occasionally applied so as to flood the whole surface. 
On May 5 there were many living prothallia and several young 
sporophytes. On June 9 there were several large, living pro- 
thallia and the young sporophytes were uninjured, although during 
the previous month the culture had been four times dry, once for 
seventy-two hours. 
SUMMARY 
As has been stated above, the experiment of subjecting pro- 
thallia to normal dry air without direct sunlight,—continuous 
conditions approximating the average of varying conditions found 
in nature,—has shown that the production of mature prothallia 
under such conditions is possible. The other experiments of 
subjecting prothallia to more thorough desiccation in the glycerin 
desiccator and over sulphuric acid show the possibility of sur- 
viving the extreme conditions found in nature. There can 
remain but little doubt that the drought-resisting character of 
the prothallia is a very effective factor in the adaptation of 
Camptosorus rhizophyllus to its habitat. 
INDIANA UNIVERSITY, BLOOMINGTON 
