June, 1923] 
MURNEEK — CHANGES IN BARTLETT PEARS 
315 
rupture is thus caused from the epidermis down into the flesh around the 
outer margin of the area of pressure. As the fruit increases in ripeness, 
much more crushing of cells of the cortex takes place. The cells adjoining 
the line of cleavage do not appear to have been pressed out of position. 
Many of them perforce are torn, or else they may be separated from one 
another along the middle lamellae. It is to be noted that in no fruit used 
in connection with this study did the area of pressure extend farther than 
the cortical region. Consequently the present histological study was con¬ 
fined to the cortex and epidermis. 
Bartlett pears, obtained from four typical orchards and employed for the 
pressure tests, were used as material. Radial sections (plugs) from repre¬ 
sentative specimens of each orchard were cut at the point of the greatest 
diameter of the fruit at the time of taking of pressure records (fig. 5). They 
were preserved in 70% alcohol. All material for microscopic observation 
was imbedded in paraffin. Radial transverse sections were cut 10 and 25 
microns thick, stained in Delafield’s haematoxylin or safranin, or in both 
for contrast, and preserved in Canada balsam. In all cases standard 
histological methods were followed. 
Results 
Upon examination of a large number of sections, it was soon evident that 
in order to show the greatest possible differences in all measurements only 
material collected comparatively early and comparatively late in the season 
should be taken into account. Hence, “early” refers here to sections 
obtained from specimens preserved on August 20, and “late” to those 
preserved on September 17. These dates indicate the greatest extremes of 
the harvesting season for the Bartlett pear in the Willamette Valley, 
Oregon, in 1920. 
Cuticle. Early in the season the cuticle is quite uniformly distributed 
over the epidermis, filling the spaces between the unevenly arranged cells. 
Opposite a comparatively wide space, formed by grouping of cells, the 
cuticle is slightly depressed or somewhat torn. As the season progresses, 
narrow cracks appear. The outer surface now becomes more uneven and 
“netted.” This condition increases as the fruit enlarges, some specimens 
showing a decidedly close-netted checking during or towards the end of the 
ripening time. Under certain circumstances these may turn into open 
cracks with slightly raised ridges. There is a general decrease in thickness 
of the cuticle. 
Table 2. Measurements of Thickness of Cuticle 
Date 
Aug. 20 
Sept. 17 
Decrease 
Ripe 
No. of determinations. 
35 
34 
15 
Thickness. 
5.8 u 
4.7^ 
19 - 0 % 
4.2 u 
