1921] 
PAYSON—MONOGRAPH OF THE GENUS LESQUERELLA 111 
or on the margins of the septum, and whenever it occurs it is 
of value to the taxonomist because of its constancy within spe- 
cific limits. One would scarcely be justified for assuming on 
any a priori grounds that any one form represented the primitive 
type from which the others have been derived, and it is with 
great interest that we notice the spherical, glabrous pods of all 
the species of this section which, because of habit and leaf out- 
line, we have already considered as primitive. In fact, to con- 
sider the glabrous, spherical pods as representing the original 
condition, and the variously elongated and compressed pods 
that are also almost without exception pubescent, as derived, is 
quite in harmony with all evidence gained from a study of the 
variation of parts about whose course of development there can 
be little doubt. 
The Septum.—When Watson proposed the genus Lesquerella 
he emphasized the characters of the septum as distinguishing 
these plants from the Old-World group, Vesicaria. Subsequent 
observation has strengthened the importance of these characters 
in limiting the genus. Although there is considerable variation 
between specles and even between individuals in the shape of 
the cells or *areolae" of the septum, there are several points 
that all the species possess in common. Of first importance, 
perhaps, is the “nerve,” or line that extends from the apex to 
near the center of the septum. The presence of this nerve is by 
no means peculiar to Lesquerella but serves to separate it from 
those genera with which it is most likely to be confused. Sec- 
ond, probably, is to be mentioned the attachment of the funiculi 
to the septum for at least part of their lengths. In some species 
the attachment is only near the base, while in others the funiculi 
are attached for over three-fourths their lengths. In all species 
the attachment is evident upon careful dissection. Here again 
the character is not peculiar to the present genus but apparently 
occurs in relatively few genera. 
Finally may be mentioned the shape of the cells of the septum. 
These vary from polygonal to tortuous, but in all the species the 
boundaries of the cells are distinct and not obscured by numer- 
ous lines that would form an anastomosing net-work over the 
surface. Neither are there present those superimposed fibers 
characteristic of some groups nor is the effect of numerous par- 
