1921] 
PAYSON—MONOGRAPH OF THE GENUS LESQUERELLA 119 
time referred to other genera, but, while they represent natural 
groups, their interrelationship seems so evident that it appears 
much the wiser course to unite them under one name. 
The first section, as previously stated, contains but a single 
species, L. Lescurii. To the second are referred but three, and 
one of these, L. frigida, has not been seen. The other two, L. 
lasiocarpa and L. Schaueriana, although united by the strongly 
obcompressed pods, show few characters in common. Probably 
intermediate species may ultimately be reported from the un- 
explored regions of Mexico. It is the third section, Eulesquerella, 
in which we are particularly interested because here occurs the 
great mass of species and because many intermediate steps are 
found between primitive and recent forms. 
The Subsectional Groups.— The aim has been to bring together 
into these groups the species that are closely allied. "They rep- 
resent, in a measure, the visible twigs of the phylogenetic tree, 
although between the units there are frequent gaps of consider- 
able extent. These groups, in some cases at least, may corres- 
pond to the ‘‘major species" of Hall and Clements. 
1. The auriculata group contains but two species, L. auricu- 
lata and L. grandiflora, and of these the first is the more primi- 
tive. Auriculate stem-leaves, annual roots, dilated filament- 
bases, and glabrous pods are their chief characteristics. 
2. The Engelmannii group has been made to include three 
species, L. densiflora, L. Engelmannii, and L. ovalifolia. The 
one unusual feature that they possess in common is a contracted 
and often subumbellate fruiting inflorescence. That the group 
is a natural one there can be no doubt. Because of the contracted 
inflorescence the first and second species might seem to be as- 
sociated, but this could not be certain were it not for the slight 
asymmetry in the stellae which both exhibit. As has been 
previously mentioned, this consists in a deeper U-shaped notch 
on one side of the otherwise symmetrical trichome. Such a pe- 
culiarity, it is believed, could scarcely have arisen twice in the 
same genus. L. ovalifolia is a rather recent segregate from L. 
Engelmannii and their affinity is very close, although the U- 
shaped notch has disappeared in the former. The three species 
may be placed in linear sequence, each having been derived from 
the one preceding. Whatever intermediates there might have 
