22 BULLETIN 365, U. S. DEPARTMENT OF AGRICULTURE. 



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 xjdem mass nearly inclose the lens-shaped phloem. There are 

 only a few rows of xjdem 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, Delphiniunh menziesii has been 

 used (PL IV, fig. 2). The stem is much smaller than that of 

 Delphinium harheyi and has a medullary lacuna much smaller 

 in jDroportion 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 gi'oup 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 DelpMnhiin cardinale (PI. Y, 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 sclerenclwma, and composed of thicker-walled cells, and 

 with a stouter structure all the way through. 



In group 4, tyj)ified by DelpJiimum recurvatum (PI. YI, 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. Delphinium geyeH was used as the type (PL 

 Y, 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 



