1921] 
PAYSON—MONOGRAPH OF THE GENUS LESQUERELLA 117 
recent forms the cotyledons are not quite symmetrical and the 
radical is slightly turned to one side. 
13. Simple or branched trichomes are believed to have given 
rise to few-rayed and finally to many-rayed stellae. 
SECTIONAL AND SUBSECTIONAL GROUPS 
An endeavor has been made to reconstruct the phylogenetic 
tree of Lesquerella from & knowledge of the tips of the branches 
with the aid of certain conclusions reached in previous para- 
graphs as to the trend of evolution (fig. 3). Such reconstructions 
are necessarily subject to many sources of error, but if they 
serve no other purpose than to present in a graphic way the 
author's conclusions, be they correct or not, they are worth 
while. Only the three main branches have been given definite 
systematic rank as sections and have been introduced into the 
taxonomic treatment. The smaller branches have been infor- 
mally termed “groups” and have been emphasized in no other 
way than by associating allied species together in the systematic 
arrangement. 
The Sections.—It is believed that there were three lines of di- 
vergence from some ancient stock. These three primary branches 
have extant one, three, and forty-eight species respectively, and 
each branch has been given sectional rank. In habit and major- 
ity of vegetative characters the most primitive species of each 
of these three sections are very similar. Only in the shape of 
the pods is there any considerable difference. In the first sec- 
tion, Alysmus, these are circular and strongly flattened parallel 
to the septum; in the second, Enantiocarpa, the outline of the 
pods in the most primitive species is also cireular but compressed 
at right angles to the partition; and in the third, Eulesquerella, 
the pods are spherical and in the more ancient species no flatten- 
ing occurs in either plane. Because from this last, or third, 
type the two others could have been more easily derived than 
the second or third type could have been developed from the 
first, or more easily than the first and third from the second, 
and because the third type has produced such an immensely 
greater number of species, it, that is, Eulesquerella, is thought 
to represent the ancient trunk more nearly than do the other two. 
Members of the first and second sections have been at some 
