1921] 
PAYSON—MONOGRAPH OF THE GENUS LESQUERELLA 121 
arenosa is more similar than L. argentea to the primitive form. 
There can be little doubt that L. macrocarpa is a recent offshoot 
from L. argentea. The reduction of its ovules to two confirms 
this belief. Within this group we see a change from annual to 
perennial habit occurring associated with a reduction in the 
number of ovules as well as the appearance of trichomes on the 
pods. There also occurs the change from sparingly pinnatifid 
leaves in L. recurvata to entire, suborbicular leaves in L. macro- 
carpa. 
7. L. angustifolia, like L. arctica, is & species without close 
relatives. The glabrous pods and abruptly dilated filament- 
bases mark it as primitive. The reduction of the number of 
ovules to two is suggestive of a longer evolutionary history. 
8. The gracilis group is characterized by the possession of a 
gynophore in the three primitive species, by sigmoid pedicels in 
all but L. gracilis itself, and by glabrous pods except in L. Pal- 
meri. This group is of particular interest on account of the diver- 
sity of form between the units involved and because three of the 
species may be thought to represent three specific generations. 
L. Lindheimeri, although inadequately known, may be regarded 
as the most primitive of the four species in the group because 
of the deeply pinnatifid leaves. The other three species, L. 
gracilis, L. Gordonii, and L. Palmeri, serve to illustrate the short- 
ening of the gynophore as specialization increases. The number 
of ovules also decreases step by step, and in L. Palmeri, in which 
this reduction reaches the average number of five, the gynophore 
has disappeared completely and the pods have become pubes- 
cent. The variety repanda of gracilis shows the appearance of 
a unique character in the genus—the shoulder at the base of 
the pods. It is not improbable that most of the succeeding 
groups have developed from this one. 
9. The pinetorum group consists of but two species, L. pine- 
torum and L. pruinosa. They are the only perennials with 
glabrous pods, sigmoid pedicels, and stellae with branched rays. 
The first shows only a partial inhibition of the terminal bud, 
globose pods, and radical leaves that are gradually narrowed at 
the base. In the second the inhibition of the terminal bud has 
become complete, the pod elongated, the basal leaves abruptly 
narrowed to the petiole, and the number of ovules reduced. 
