20 BULLETIISr QQo, V. S. DEPAETMEXT OF AGEICULTUEE. 



pericycle consists of a ring of sclerenchymatous tissue bet^veen 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 fibere, 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 parenchj^ma. 



Classified according to cross sections of stems, the 29 species of 

 Delphinium examined fall into six groups, as follows : 



Group 1. Delphinium harbeyi, D. calif ornicum, D. cucullatum, D. geranii- 

 Jolium, D. glaucum, D. occidentale, D. roMistum, D. sapellonis, D. scopulorum, 

 D. troliifolium. 



Gi'Oiip 2. Delphinium andersonii, D. hicolor, D. decorum, D. depauperatum, 

 D. menziesii, D. midicaule, D. tricorne. 



Group 3. Delphinium blocJwiannw, 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. consoUda. 



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, ajid in general represents those species known 

 as low larkspurs. Section III consists of gi'oup 6, the European 

 consoUda group. 



Delphiniimh harbeyi has been taken as the type of group 1. 

 Figure 1, J., is a diagram of a cross section of a stem D. hm^heyi, 



