4 BULLETIN 1072, U. S. DEPARTMENT OE AGRICULTURE. 
it from the trees early. In the present practice the size of the fruit 
is the most important consideration in determining when to pick. 
In the investigations here recorded special attention has been paid 
to the time of picking the fruit. Pickings of pears have been made 
at intervals beginning before the commercial season started and 
continued until some time after it was over. Observations of the 
fruit have been supplemented by chemical studies, the results of 
which have been presented in a previous report. 3 Tests of the out- 
put of carbon dioxid from the fruit following picking at different 
stages of maturity and under different temperatures of storage have 
also been made and will be reported in detail in a separate publica- 
tion. The exact analyses upon which many of the conclusions 
reached in this report are based have been presented in detail in the 
paper mentioned. 
There is no fixed time at which it may be said that pears are in 
just the right condition to pick. The time of picking will vary 
widely with the manner in which the fruit is to be marketed. 
If removed from the trees too early. Bartlett pears will tend to 
shrivel and wilt before ripening. It has been found that the time 
at which the fruit may be picked without danger of wilting can be 
determined by testing for the corking over of the lenticels. 
As the fruit grows, numerous small light-colored spots can be 
observed all over its surface. Examination under the microscope 
reveals the fact that these are minute openings through the skin of 
the fruit. These lenticels. as they are called, are open during the 
early growth of the pears. If such a fruit be immersed in a strong 
solution of metlrylene blue in water and left for 15 minutes to half 
an hour, these spots will be colored a deep blue by the stain that 
has penetrated the tissue. About the time shipping usually com- 
mences, however, the lenticels become brown, owing to the formation 
of a layer of corklike cells over the surface of the opening. After 
this forms, if the fruit is immersed in the methylene-blue solution, 
the stain penetrates very little. TThen the fruit is removed from the 
stain and rinsed, the methylene blue can be detected only as a faint, 
thin ring about the outside of the lenticel. The stain will not 
penetrate the corky layer. Although it has never been tested, it 
is extremely probable that ordinary laundry bluing, made up in a 
strong solution, would serve the purpose as well as methylene blue. 
After the lenticels are once sealed over, there is little further 
danger of the fruit shriveling after removal from the tree, and if it 
has attained sufficient size it can be picked with safety. It has been 
found, however, that if the fruit is left on the tree for about two 
weeks longer, a very much superior product will be obtained. The 
sugar content increases rapidly during this period, and the fruit is 
3 Magness, J. R. Op. tit. 
