330 PicKETT: A STUDY OF CHEILANTHES GRACILLIMA 
FIELD AND LABORATORY INVESTIGATION 
Examination of C. gracillima at different seasons of the year 
shows the following items aside from the developmental history, 
which is given later. The most vigorous growth is in the spring, 
March to May. Fronds are persistent through the summer and 
to some extent into the second summer. With the advent of 
summer and the reduction of both atmospheric and soil moisture 
the fronds and individual pinnae are closely curled together. 
They take on a blue-gray appearance, and are harsh to the 
touch, like herbarium specimens. The rootstocks are buried 
under a few inches of light soil in the rock crevices but are quite 
dry in midsummer. The roots are small, fibrous, covered with a 
definite corky layer, and extend sometimes as far as four or five 
feet through the crevices in the rocks. An ee growth of 
new roots is produced by the rootstocks each s 
On August 10, 1921, mature, fertile fronds were age for 
cultural work. Although mature, these fronds had lost but few, 
if any, of their spores when collected. They were placed in 
paper folders and stored in the laboratory. When the folders 
were opened on November 27, but very few loose spores were 
found, and examination showed the sporangia unopened, almost 
without exception. After being in water for an hour some fronds 
were placed on filter paper in a desiccator over night. When 
examined the next morning the paper was well covered with 
spores. By repeating this process three or four times it was 
possible to empty nearly all the sporangia. 
On November 28, 1921, several cultures were started by 
sprinkling spores over dishes of Knop’s solution, one-half usual 
strength, over dishes of agar agar made up with one-half strength 
Knop’s solution, and over sterilized soil in perforated clay 
saucers. The spores germinated freely after ten to twelve days, 
and by December 17 germination had proceeded far enough for 
the cultures to show a distinct green surface. Differences of 
temperature through a fairly wide range, 45°-70° F., seem 
make no appreciable change in the rate or percentage of germi- 
nation. 
The spores of this plant are nearly spherical with their clearly 
marked sutures between pairs of thickened, rounded ridges 
Fic. 1). They show marked variability as to size, measuring 
