488 
F. L. PICKETT 
the case of Camptosorus. The same culture methods have been used, 
and the same apparatus for securing extreme conditions. In fact 
cultures have been kept along beside those of C. rhizophyllus , and in 
the desiccation experiments tubes containing the two plants were 
attached in series so that they received exactly the same exposure. 
The important differences in treatment were in the experiments 
involving varying light conditions. 
Fronds were collected June 24 and October 18, 1913. The latter 
collection was of fronds grown up after the rain of September 12. 
Cultures were prepared on soil, also on culture solutions as described 
in a later paragraph. The following features in the germination 
and development may be stated as generally true. The growth of 
the prothallia is much more uniform than in the case of C. rhizophyllus, 
although on soil cultures it is not unusual to find germinating spores 
and plants with twenty-celled plates side by side. The prothallia 
grow rapidly and symmetrically in either sunlight or full diffuse light. 
In twenty days after the spores are sown plants of five to fifteen cells 
may be found. At the end of ten weeks most of the plants show 
mature antheridia and archegonia. These points are true for cultures 
grown at an average temperature of 21° C. Only after the plants were 
sexually mature have they been subjected to the various conditions of 
experiment touching resistance to desiccation and low temperature. 
Extreme Desiccation. — Plants were exposed to dry air in the desic- 
cating apparatus with the following results: 
I. Glycerine desiccator all dead after 6-7 days. 
II. Sulphuric acid tube " " " 6-7 " 
III. Calcium chloride tube " " " 5-6 " 
IV. Freseniu. -calcium chloride " " 5~6 " 
V. Fi-esenius-sulphuric acid " " " 5-6 " 
The variable time of 5-6 and 6-7 days in these items is so placed 
because quite regularly a few plants of average size and normal 
appearance, have been found living after the shorter exposure. The 
writer is inclined to consider this a demonstration of remarkable 
individual variation in this respect comparable to that shown by the 
prothallia of this plant to a very unusual degree in other ways, to be 
noted later. 
Extreme Natural Conditions. — Cultures allowed to become dry in 
the greenhouse showed no damage after three weeks, in diffuse light. 
