152 THE AMERICAN MIDLAND NATURALIST 
southern drainage of the Missouri River. Simpson reports it for 
the Mississippi drainage generally. A three hundred mile survey 
of the Osage River, beginning at the headwaters, reveals the shell 
of this species in all its external form and nacre-color extending to 
granifera and even including Pleth. cooperianus. Variation in nacre- 
color for this species is remarkable; however, this deviation from the 
unipurple nacre of the type may be due to local reaction since it is 
most noticed in the Osage below the region of medicinal springs. 
Its favorable habitat is that of rocky shoals, but is occasionally 
found in deep, quiet water with mud bottom where it acquires a 
smoother, heavier and less inflated shell. The writer has had the 
good fortune to secure, for the first time, several individuals gravid 
with mature glochidia. ‘The larva is found to be somewhat smaller 
than that of Rk. granifera and with hinge line shorter and straighter; 
as to form, and even as to size, it is hardly distinguishable from 
granifera when allowance is made for variation in a large series. 
This glochidium is figured and described here for the first time (See 
Plate I, Fig. 4). It is observed by the writer to be gravid from June 
until the middle of August, bearing ripe glochidia mostly about 
the middle of July. It is decidedly a short period breeder. 
(To be continued.) 
ENUMERANTUR PLANTAE DAKOTAE SEPTEN- 
TRIONALIS VASCULARES.—I. 
ae e 
ENUMERAVIT J. LUNELL. 
The Vascular Plants of North Dakota.—I. 
With Notes by J. Lunell. 
INTRODUCTORY. 
The statements and data furnished in the following series 
of papers are derived substantially from a twofold origin: (1) My 
own herbarium, a part of which contains the visible results of 
my wanderings in this state during the years of 1889 to 1914 
(except 1897 and 1903, when field work in the state of Oregon 
and in Europe attracted my exclusive attention); and (2) My 
Panama-Pacific Exposition Herbarium of North Dakota, which 
contains a rich supply of its own habitational informations, and 
