1917] FAUST—RESIN SECRETION 455 
features of the stone cells deserve special consideration. These 
cells are found principally in the hypodermal region and give a 
hardness to the cortex, which makes untreated material difficult to 
section. They take on a vivid green with the malachite stain. 
They are somewhat larger than the surrounding cortical paren- 
chyma, due to their thickenings. In surface view they present a 
polygonal appearance, with bluntly rounded corners (fig. 19, a—d). 
A view at the edge of the cell shows circular pores which enlarge 
and approach one another as they invade the center of the cell. 
The center of the cell is an irregular space devoid of the sclerified 
material, usually filled with ordinary parenchyma cell protoplasm. 
This content fails to react to starch, oil, or resin tests. As the 
canals of the cells near the lumen, they anastomose in pairs or 
triplets, giving an appearance as shown in fig. 19,d. The cells have 
at least one transverse diameter longer than the longitudinal (com- 
pare fig. 19, c with d). This same type of stone cells also occurs in 
the axial plate of old woody roots (both primary and secondary), 
and in the wood of subsequent formation, although it is never found 
in phloem regions. In the latter tissues it is supplanted by bast 
strands (fig. 13). The stone cells usually occur in groups of five 
or six. 
STEM AND PEDUNCLE.—The hypocotyledonary stem contains the 
tetrarch arrangement, as shown in fig. 20. The phloem is exarch 
- and the xylem endarch, with protoxylem innermost. As progress 
is made up the stem, the meristematic region where the bud resides 
is approached, containing secondary stem, leaf, and flower structure. 
At this place the four main strands each give off two anastomosing 
bundle strands to the bud, while the major portion of the bundle 
strands continues into the cotyledonary collar (fig. 21). Slightly 
above the section diagrammed in this figure certain changes occur 
in the bundle strands. These are best illustrated by a comparison 
of the section shown in fig. 22 with fig. 24, a diagram of the course of 
the bundles, seen longitudinally. Between levels cc and dd strands 
are given off from w and x, which unite above dd to form a median 
strand ~. Coincidentally laterals from y and z form the median 
strand s. Similarly above the section dd, x and y, z and w, give off 
subsidiary strands which anastomose in pairs to form respectively 
