THE PROPORTION OF PARTS IN FRUITS 315 



or pericarp during this period ; and, as in the case of the 

 seed, the two sets of observations for 1908 and 19 10 tell a 

 similar story. In the third week of September, when the 

 shell had reached the height of its growth, it was moist, 

 almost fleshy inside, and about 2 millimetres thick. After 

 this it began to turn brown, lose weight, and to dry, signs 

 of the severance of its vital connections that antedated those 

 of the seed. Whilst the seed had been getting larger, heavier, 

 and more solid, its shell had been getting thinner and drier, 

 so that when the acorn was ready to fall from its cupule, 

 its well-browned shell had lost more than half its original 

 thickness and much of its water. Such are some of the 

 changes in relation between the seed and shell of the acorn 

 illustrated in the table. They are still more evident when 

 we handle the ripening acorns on the tree. 



On looking at the general table given on p. 303 showing The general 

 the proportions by weight of the pericarp and seeds during as^the'fruit^ 

 the early growth, maturation, and subsequent drying of a ^^^^ures and 

 variety of fruits, it will be noticed that as a general rule from dries, the 



, f. ,, -I- 1 1 proportion of 



the young rruit on the plant with immature seeds, to the the pericarp 



withered-up fruit, as it lies on the ground, there is a con- and^that^of 



tinuous decrease in the proportion by weight of the pericarp, the seeds 

 fi •'o rrj increases, 



and a continuous increase in that of the seeds. In some 



fruits, it is true, as in the capsule of Iris fcetldissima and in 

 the fruit of the Coco-palm, the proportional amount of the 

 pericarp in the completely dried fruit is rather more than in 

 the earlier drying stage, a result due to the seeds losing weight 

 less readily at first, as explained below. But this does not 

 seriously affect the general trend of the figures ; and it is 

 very probable that in the majority of fruits of the type of 

 the capsule and the legume the general decrease in the pro- 

 portional weight of the pericarp, as the fruit grows, matures 

 and dries, would not exhibit any such interruption. 



It is a familiar fact of observation that the earlier history Illustrations 

 of a fruit's development is mainly concerned with the fruit- principle. 

 case and the later history with the seed. Nothing short of 



