474 Journal of Agricultural Research voi. xix. No. lo 



the outside becomes yellow; or, if the inside does remain sound, it 

 becomes coarse and granular and has a very inferior texture. 



However, in most sections there is a period of from six weeks to over 

 two months between the time at which the first commercial picking is 

 now made and the time the fruit becomes ripe on the tree. Conse- 

 quently, there is a possibility of considerable variation in the time at 

 which the fruit may be removed from the tree in a green, firm condition 

 and still ripen without shriveling. A consideration of these facts shows 

 the importance of knowing what effect removing the fruit from the 

 tree at varying times has on the keeping quality and on the comparative 

 chemical composition from which the food value and eating quality may 

 be judged. 



REVIEW OF LITERATURE 



Of much interest in this connection is the work of various investi- 

 gators who have studied the chemical composition of pears. Some studies 

 have been made of the influence of various environmental factors on the 

 chemical composition of the fruit, which are of sufficient interest to war- 

 rant discussing in some detail. 



Kulisch (7) concluded, among other things, that the age and shape 

 of the tree and the size of the crops borne have an effect on the compo- 

 sition of the fruit. He found higher sugar content and larger size of 

 fruit correlated in trees that had a light crop as compared to those with 

 a heavy yield. He suggests that with a light crop there is an abundance 

 of carbohydrate material for the full development of the fruit, while a 

 heavy crop tends to draw from other organs of the tree, and even then 

 the crop is cut down in size by an insufficient amount of carbohydrate 

 material. 



Ewert (4), in studying the influence on the fruit of the presence of 

 well-developed seeds as compared to parthenogenetic fruit, made analy- 

 ses of both kinds in several varieties of pears at intervals just previous 

 to and including the time of ripening. In the late fall varieties with 

 which he worked he found a marked increase in sugar as both seeded 

 and seedless pears approached maturity, while the acids appeared to 

 fluctuate somewhat. He found very little starch present in either 

 seeded or seedless fruit. Cane sugar was very rarely present in ripe 

 pears in the varieties studied. He found no very marked and constant 

 differences due to the presence or absence of seeds, the results in this 

 respect apparently varying with the variety. 



Kelhofer (6) analyzed the various portions of the fruit of one variety, 

 Siebenmannsbienen, for sugar, acid, and taimin. He found both sugar 

 and acid to be higher in the central flesh portion as compared to the outer 

 or peel region and the inner or core region. The greatest amount of 

 tannin was in the outside or peel region, and there was very little in the 

 core region. Analyses at succeeding dates from time of picking until soft 

 ripe show a^ slight gain in sugars, a marked loss in acid, and a very marked 



