20 
pericycle consists of a ring of sclerenchymatous tissue between the 
cortex and the phloem portion of the fibrovascular bundles, and is 
composed of the bast fibers of the bundles and the interfascicular 
sclerenchyma. The cells of the pericycle have thickened walls, es- 
pecially in the case of the bast fibers, the cells of which are also 
smaller than those of the interfascicular sclerenchyma. Inside the 
pericycle are the phloem and xylem portions of the fibrovascular 
bundles, the bundles being separated by the medullary rays, which 
are as wide as the bundles, and the cell-walls of which are some- 
times thickened so that they are not distinctly marked off from the 
pericycle. The medullary rays are continuous with the medullary 
portion of the stem, in which there is a medullary lacuna of varying 
size. 
The fibrovascular bundles are of the closed collateral type, ar- 
ranged in a single circle, just inside the cortex. In this description 
the bast fibers are considered as part of the fibrovascular bundle. 
The group of bast fibers seen in cross section varies from a wedge 
shape to a somewhat circular shape, and is usually not sharply de- 
fined from the interfascicular portion of the pericycle. It partially 
incloses the phloem and cambium, while the curved outer border of 
the xylem partially incloses the cambium on the inner side. The 
phloem consists of sieve tubes and small companion cells. The 
cambium is composed of several rows of small thin-walled cells, 
elongated tangentially, lying in a curved line, with the convexity 
toward the xylem. Between and surrounding the tubes of the xylem 
proper is a varying amount of xylem parenchyma. 
Classified according to cross sections of stems, the 29 species of 
Delphinium examined fall into six groups, as follows : 
Group 1. Delphinium baroeyi, D. californicum, D. cucullatum, D. geranii- 
folium, D. glaucum, D. occidentale, D. robustum, D. sapellonis, D. seopulorum, 
D. troliifolium. 
Group 2. Delphinium anclersonii, D. bicolor, D. decorum, D. depauperatum, 
D. menziesii, D. nudicaule, D. tricorne. 
Group 3. Delphinium blochmannw, D. cardinale. 
Group 4. Delphinium carolinianum, D. recurvatum, D. simplex, D. variegatum, 
D. variegatum apiculatum. 
Group 5. Delphinium geyeri, D. scaposum, D. virescens. 
Group 6. Delphinium ajacis, D. consolida. 
These six groups may be combined in three main sections. Section 
I includes only group 1, which comprises all the species which are 
commonly known as tall or giant larkspurs. Section II includes 
groups 2, 3, 4, and 5, and in general represents those species known 
as low larkspurs. Section III consists of group 6, the European 
consolida group. 
Delphinium oarbeyi has been taken as the type of group 1. 
Figure 1, A, is a diagram of a cross section of a stem D. barbeyi. 
