PLATE 6 
Histological studies of the regions of elongation in sunflower, Paris daisy, and sweet 
pea showing how inoculations in these regions might involve a number of intemodes. 
A. —A longitudinal section of the region of elongation of a sunflower. An inocula¬ 
tion puncture in this region frequently penetrates the area indicated by the circle at 
the base of the arrow which represents the diameter of the needle used. Intercellular 
spaces have been found extending upward throughout the distance covered by the 
arrow in the pith, and even further in the cortex. This distance is occupied by fifteen 
to twenty intemodes. A cross section of the tip made at a position corresponding to 
the line a is shown in B. X8. 
B. —A cross section made through the region of elongation of a sunflower at a position 
0.13 mm. behind the apical cell corresponding to the line a in A. Three of the 
outermost leaves have been removed. Intercellular spaces were found in the regions 
marked b and c. X8. 
C. —Camera lucida drawing showing the intercellular spaces in the leaf primordia 
in the position marked b in B. X$ia. 
D. —Camera lucida drawing showing the intercellular spaces in the pith in the posi¬ 
tion marked c in B. X512. 
E. —Similar to A, except made through the region of elongation of a Paris daisy. A 
cross section of this region revealed a situation similar to that found in the sunflower 
as shown in B, in regard to condensation of the intemodes and the occurrence of 
intercellular spaces. At 0.14 mm. from the apical cell intercellular spaces were found 
in the pith. X48. 
F. —Similar to A, except made through the region of elongation of a sweet pea. 
In this case there are not so many intemodes in the region of elongation as in the sun¬ 
flower and Paris daisy. The circle at the base of the arrow indicates the relative size 
of the needle used. Intercellular spaces were found at 0.18 mm. from the apical cell. 
X32. 
The photomicrographs shown in this plate were made from paraffin sections colored 
with Flemming’s triple stain. In each case the hairs about the young leaves have been 
blocked out. 
