24 BULLETIN" 365, U. S. DEPARTMENT OF AGRICULTURE. 
Group 6 is represented by Delphinium ajacis (PL VI, fig. 2, and 
fig. 4, A and B). The stem is circular and has a relatively small 
medullary lacuna. The bundles are about 46 in number and are of 
two sizes, the large and small arranged alternately. This is the only 
group in which it was possible to distinguish a row of endodermal 
cells. All the cell walls are much thickened, which is a distinguish- 
ing characteristic of this group. The shape of the fibrovascular 
bundles is quite characteristic. The bast is wedge-shaped, composed 
of cells whose walls are so thickened that the lumen is reduced almost 
to a point. The phloem is small and completely inclosed by the 
bast and xylem. The xylem mass is larger than the bast, elongated, 
and includes a large amount of xylem parenchyma. 
Delphinium consolida is similar to D. ajacis, but the bundles are 
less numerous, the cell walls in the pericycle are thickened still 
further, and part of the cells of the cortical parenchyma have thick- 
ened walls. 
Any of the species which were examined could be quite easily 
placed in one of the above groups, but within the groups the work 
thus far done has not revealed sufficiently characteristic differences 
in stem structure to make identification of species possible. Vesque, 
1881, page 29, says that while it is impossible to distinguish genera 
by anatomical characters, it is easy to distinguish species, but he 
uses different characters to differentiate the species, such as the struc- 
ture of the petiole, the development of palisade cells, and the dis- 
tribution of stomata in the leaf. On the other hand, the present 
work is based on stem characters, which serve to differentiate be- 
tween genera in the family Kanunculacese, and in this case between 
groups of species in the genus, but not between individual species. 
An exception to this is group G, of which we have only two species 
in America, and these two can be distinguished by the anatomy of 
the stem. These two are European species which have been intro- 
duced into the United States, and are described anatomically by 
Lenfant (1897, pp. 26-27, PL VII) and Marie (1885, pp. 117-118, 
PL VI). The specimens of ajacis and consolida from the Na- 
tional Herbarium which were examined had evidently been mis- 
named, one for the other, as was discovered by comparing cross sec- 
tions of the stems with the descriptions and figures of Marie and 
Lenfant. 
Sections were also made of two species of Aconitum, A. bakeri 
Greene (PL VI, fig. 3 ; and fig. 5, A and B) and an unidentified species 
from California, in order to compare them with and to differentiate 
them from the tall larkspurs. The cross section of the stem shows a 
structure similar to that of the tall larkspurs, but it can be easily 
distinguished by the lack of a medullary lacuna, and by the complete 
