338 Pickett: A sTUDY OF CHEILANTHES GRACILLIMA 
structures isso like the development of new tissue by injured liver- 
worts as to be quite striking. Fics. 29-33 show various types. 
From work so far done the seasonal history of C. gracillima 
is as follows:—In the early spring sterile fronds are produced. 
These are followed in June by fertile fronds. The spores are 
matured before the winter’s moisture has entirely left the 
scant soil in the rock crevices where the fronds grow. Aside 
from periods of very slight showers the fern remains inactive 
until late summer or early autumn. The fronds become dry and 
curl up closely, but, contrary to the usual habit of ferns, they do 
not lose their spores. With the coming of the first autumn rains, 
alternating with days of bright, warm sunshine and dry winds, 
the sporangia open and the spores are scattered. These spores 
germinate during the brief periods of sufficient moisture and lie 
quiescent during periods of drought, and so through considerable, 
broken growth-periods they are able to reach maturity and pro- 
duce sporophytes. This may take place through the fall, winter 
and succeeding spring, or the prothallia are capable of living 
through one dry summer season before producing any sporophytes. 
SUMMARY 
In conclusion the following points should be noted. Chei- 
lanthes gracillima is a typical xerophytic fern, owing its dis- 
tribution and maintenance of habitat to a great extent to pecu- 
liarities of the gametophyte generation. 
Spores and prothallia of this fern survive long periods of desic- 
cation without any evidence of means for preventing the loss of 
water. Spores are retained after maturity until fall or winter. 
: Prothallia are strictly dioecious with marked differences 
in form and size of antheridial and archegonial plants. 
Prothallia survive the usual winter conditions of eastern 
Washington. Marked development of vegetative propagation 
of prothallia is shown. 
All figures used are from camera lucida drawings. Fics. 
26-33 are from drawings by Miss Lotta Dueber, a graduate 
fellow in the Botany Department for the year 1922-23. Miss 
Dueber should also be given credit for her care of cultures 
during that year. The other figures used are from the author's 
drawings. 
Tue State COLLEGE oF WASHINGTON, | 
PULLMAN, WasHINGTON 
