June, 1923] 
MURNEEK — CHANGES IN BARTLETT PEARS 
317 
quite conspicuously from those underlying them, being much smaller and 
more flattened. Stretched tangentially and plate-like in form, they are 
more evenly arranged and more closely united with each other than are 
those of the epidermis. There appears to be no thickening of the outer 
walls. Subepidermal cells of the first layer show a proportionally faster 
seasonal increase in tangential than in radial diameter. The resultant 
enlargement in size, as measured in one plane, is close to 40% (table 5). 
This perhaps is a good indication that subdivision of cells is much less 
frequent here than in the epidermis. 
Table 5. Measurement of Cells of Subepidermis {second layer below epidermis) 
Ave. Diam., 
Tangential 
Ave. Diam., 
Radial 
Approx. Area 
Long. Sect. 
Increase 
No. of determinations. . * . 
80 
80 
August 20. 
18.2 ,U 
12.2 /jl 
224 sq. n 
September 17. 
22.2 fj, 
I4.O M 
312 sq. fj. 
39 - 3 % 
Second to fifteenth layers. As a rule, cells of the subepidermal region, as 
far as the fifteenth layer, are considerably smaller and more compact than 
those of the cortex proper (fig. 6). Observation showed, however, rather 
gradual but quite conspicuous increments in size from the periphery in¬ 
ward. Most probably the enlargement is at the same rate in all diameters. 
From measurements in 1920 it appears, however, that a relatively greater 
increase had taken place in the radial diameter, the cells having rounded 
out and become more nearly isodiametric. No difference in thickness of 
walls on the peripheral side of the cells could be noted. 
Table 6. Measurements of Cells of Subepidermis {3d to 5th layer below epidermis) 
Ave. Diam., 
Tangential 
Ave. Diam., 
Radial 
Approx. Area 
Long. Sect. 
Increase 
No. of determinations.... 
80 
80 
August 20. 
26.5 n 
16.8 fx 
445 sq. n 
September 17. 
33-5 M 
22.0 n 
737 sq. n 
65-6% 
Within the subepidermis are scattered groups of a few to a dozen or more 
sclerenchymatous or stone cells (fig. 7). Occasionally single isolated cells of 
this type are found imbedded in this region. Although the sclerenchymatous 
cells of the subepidermis are conspicuous enough in the Bartlett, Zschokke 
(19) found them to be so numerous in some late varieties of pears as to form a 
shell as it were around the fruit. No seasonal change in distribution of 
stone cells could be detected, though naturally they become somewhat more 
