1921] 
PAYSON—MONOGRAPH OF THE GENUS LESQUERELLA 105 
species. In it the rosette is fully developed. Not because of 
any arguments to be derived from the condition of the roots 
themselves, have the present phylogenetic conclusions been 
reached, but because of the correlation with these habits of 
various other characters that seem clearly to point the direction 
of the current. The appearance of the rosette habit among the 
perennials, a character that is clearly derived from the normal 
condition found in the annual species, is one argument in favor 
of the present hypothesis that the ancestor of this genus was 
quite devoid of woody tissue and if not a true annual, was at 
least entirely herbaceous. 
Shape of the Leaves.—In the form of the leaves, and particu- 
larly of the radical leaves, are to be found some of the most con- 
vincing bits of evidence that point the direction in which evolu- 
tion has occurred. Pinnate, and especially lyrate-pinnatifid, 
leaves are common throughout the Cruciferae, and for this rea- 
son alone one would be inclined to consider those species bearing 
this type of leaf as more primitive than those with entire leaves. 
It is among the annual species that the pinnate leaf finds its 
best development, and, indeed, there are none of the purely 
herbaceous species, except L. Cusickii, that do not exhibit this 
tendency to a more or less marked degree. On the other hand, 
in only three or four perennial species is the lobing of the radical 
leaves at all conspicuous. The change from one type to another 
is very gradual, and the same species may sometimes have entire 
and sometimes lyrate leaves. Two distinct tendencies are noted: 
either the leaf may become narrower until a truly linear form is 
attained, as in the alpina group, or it may become broader and 
the blade abruptly, rather than gradually, narrowed to the peti- 
ole. Four species in the genus have cauline leaves that are 
definitely auriculate at the base and conspicuously toothed. 
These four species are distributed within the three sections, are 
all annuals, and all have pinnate basal leaves. Such a condition 
is believed to represent the ancestral type, and from it to have 
been derived linear or suborbicular radical leaves and oblanceo- 
late or linear cauline leaves with a narrow base. 
The Flowers.—In this, as in most other genera of the family, 
there are few differences in flower parts that offer characters of 
taxonomic value or help to solve the intricacies of phylogeny. 
