22 BULLETIN 365, U. S. DEPAETMEXT OF AGEICULTUEE. 
number, and rather small in proportion to the diameter of the stem, 
those at the angles being a little larger than the others. The cross 
sections of the xylem and the bast are about the same in size, both 
being somewhat circular in form. The horns of the bast mass and 
the xylem mass nearly inclose the lens-shaped" phloem. There are 
only a few rows of xylem parenchyma at the inner end of the xylem. 
The walls of the cells of the pericycle are not very greatly thickened. 
The bast fibers of the bundles lying between the angles of the octagon 
are separated from the cortex by one or two rows of cells continuous 
with the interfascicular sclerenchyma. 
As a type of the second group. Delphinium menziesii has been 
used (PI. IV, fig. 2). The stem is much smaller than that of 
Delphinium ~barl>eyi and has a medullary lacuna much smaller 
in proportion to the diameter of the stem. The circumference of 
the stem is practically circular. The bundles are about 24 in num- 
ber, of two sizes arranged alternately. The fibrovascular bundle 
exhibits in cross section a form quite distinct from that of group 1. 
The bundle is longer and narrower, the bast being wedge-shaped 
with the larger end situated externally. The phloem portion of 
the bundle is open laterally, the inner boundary of the bast and 
the outer line of the xylem being only slightly curved. The xylem 
proper is small in extent, but there is a large amount of xylem 
parenchyma extending toward the medullary lacuna. 
Group 3 is represented by Delphinium cardinale (PI. V, fig. 1), 
and in type of stem structure can not be differentiated from group 
2. The group 2 type is here exhibited on a larger scale, with a bast 
larger in amount, and more sharply differentiated from the inter- 
fascicular sclerenchyma. and composed of thicker-walled cells, and 
with a stouter structure all the way through. 
In group 4, typified by Delphinium recurvatum (PL VI, fig. 1), 
we have a stem structure which may be considered as intermediate 
between the true low larkspur type of group 2. and the taller forms 
represented in group 5. The general form of fibrovascular bundle 
corresponds to that of group 2, but the stem is more compact in 
structure, the bundles longer and arranged more closely, and the 
alternate large and small bundle arrangement less prominent. 
For the fifth group. L)elphinium geyeri was used as the type (PI. 
V, fig. 2, and fig. 3. A and B). The medullary lacuna of the stem 
is very small and the external circumference approaches the octago- 
nal. The bundles are about 30 in number, those at the angles 
being slightly larger than the others. The cells of all the tissues of 
the stem are relatively small and numerous. The fibrovascular 
bundle is similar in the form of cross section to that of group 2, but 
is larger and much elongated, the bast in particular being very ex- 
tensive. The bast is oblong to wedge-shaped, and composed of very 
