16 BULLETIN 1073, U. S. DEPARTMENT OF AGRICULTURE. 



cent. Puebla, Lyon, Dickinson, and Blakeman have less than 1.25 

 per cent, Fuerte being the only variety to exceed that amount. 



CORRELATION BETWEEN MATURITY AND COMPOSITION. 



Even a superficial study of the tabulated data reveals many inter- 

 esting relations between the composition of the fruit and its maturity. 

 The greatest problem in maturity investigations, however, is the 

 correlation between physical appearance and composition. As a rule 

 it is not hard to decide fairly accurately from its composition at what 

 stage of growth a fruit is in its optimum condition. It is compara- 

 tively difficult, however, to correlate this stage with some physical 

 aspect, particularly when the optimum condition desired necessitates 

 the gathering of the fruit some time before it is to be eaten or pre- 

 served. All fruit reaches a stage where its maturity is manifest from 

 the physical appearance, but usually when this stage is reached the 

 fruit has passed the optimum condition for long shipment and per- 

 haps even for storage. For instance, when cantaloupes have begun 

 to develop a yellow color on the vine, the time is past when they can 

 be satisfactorily shipped for long distances, and coloring on the tree 

 marks the time when Bartlett pears have passed their best condition 

 for shipping and storage. 



Purple or black avocados change in color during growth. An ex- 

 tended study of these varieties might show some correlation between 

 their color and their composition. In the case of green-colored fruit, 

 however, such an opportunity is not afforded. Neither kind can be 

 left on the tree until soft enough to eat, with satisfactory results, for 

 besides the loss of time there is also a noticeable loss in flavor. 



The color of the stem has been suggested as an indication of 

 maturity. This may be practical with some varieties, but so far 

 the experience of the authors has led to no definite conclusions in 

 this matter. The stems of some decidedly immature fruit are yel- 

 lowish, while those of others are green after the fruit has reached 

 a satisfactory state for picking. As far as physical appearance is 

 concerned, it has been impossible to correlate closely any single 

 character or set of characters with maturity. 



There is, however, a definite correlation between some other char- 

 acteristics and ripeness. Thus, the time which elapses after picking, 

 until the fruit becomes sufficiently soft to be edible, roughly indicates' 

 whether or not it was in a satisfactory condition when picked. Data 

 in Table 4 show that during growth there is a sharp decline in the 

 time necessary for this softening, but the chart (fig. 1) shows that 

 this change is seldom correlated with the fat content. For instance, 

 in the case of the Fuerte, in February the period elapsing between 

 the time of picking the fruit and the time when it was soft was only 

 6 days, whereas before that time this period had been from 11 to 16 



