[KIRSCH] ORIGIN AND DEVELOPMENT OF RESIN CANALS 87 
Fig. 5.—Pinus banksiana. Radial section of a shoot collected June 28, 1907, 
showing a medullary ray ,m.r., running from the phloem, pl.,to the protoxylem, pr. 
x.; and the connection with a strand of parenchyma cells containing a canal r.c. x 140. 
Fig. 6.—Pinus banksiana. Radial section showing a medullary ray, m.r. going 
from the bast, ph., to the wood, x. In the bast the central cells of the ray are divid- 
ing rapidly in all directions. x 372. 
Fig. 7.—Pinus banksiana. Radial section showing a fusiform ray, m.r., con- 
taining a resin canal, r.c. which ends in a resin cyst, r. cy. in the bast. x 372. 
Fig. 8.—Pinus banksiana. Radial section showing two medullary rays, m.r., 
in contact with a vertical strand of wood parenchyma cells, pa. s. x 372. 
Fig. 9.—Cupressus goveniana. Radial section showing a vertical strand of 
resin cells, pa. s. given off from a medullary ray, m.r. x 322. 
Fig. 10.—Pinus strobus. Cross section through cambial region, ca., showing 
the connection between a strand of parenchyma cells pa. s. and medullary ray, m.r. 
x 644. 
Fig. 11.—Pinus strobus. Cross section through the cambial region illustrating 
the initiation of a medullary ray, m.r., just previous to the formation of a vertical 
strand of parenchyma cells, pa. s. x 644. 
Fig. 12.—Pinus banksiana. Cross section showing two strands of parenchyma 
cells, pa. s., in contact with a medullary ray, m.r., x 644. 
Fig. 13.—Pinus banksiana. Cross section showing beginning of schizogenous 
space r.c., in a group of parenchyma cells. x 644. 
Fig. 14.—Pinus banksiana. Showing resin pasage, r.c., taking on its character- 
istic form. x 644. 
Fig. 15.—Pinus banksiana. Cross section from same shoot as that of Fig. 14, 
only slightly higher up. Shows same canal r.c. as Fig. 14, but no connection between 
the parenchyma cells and a meduilary ray. x 644. 
Fig. 16.—Pinus banksiana. Cross section showing the elements of a medullary 
ray, m.r. functioning as epithelial cells, ep. of a vertical resin passage, r.c. x 644. 
Fig. 17.—Pinus banksiana. Radial section near protoxylem showing elements 
of a medullary ray, m.r. abutting on a resin passage, r.c. and functioning as epi- 
thelial cells, ep. x 644. 
Fig. 18.—Pinus strobus. Radial section showing a medullary ray, m.r. giving 
cells to a resin passage, r.c. x 248. 
Fig. 19.—Pinus strobus. Cross section showing an aggregate of parenchyma 
cells containing a resin canal, r.c., at the border of the spring, sp.w., and summer 
s.w., wood. x 644. 
Fig. 20.—Pinus banksiana. Cross section, two views of the same medullary 
ray, m.r. at different levels in the shoot. x 140. 
