FRUITS AND SEEDS 237 



are objects of attainment. It has so far not been proved that 

 a fruit will develop many new cells during its growth to 

 maturity. This may take place to a limited extent ; but from 

 the fact that large fruits do not contain many more cell-layers 

 than small fruits of the same variety, we may assume that the 

 differences in fruits are mainly due to a difference in the 

 development of the cells. The size of the cells, however, 

 and the amount of their contents are exceedingly variable. 

 The development of the fruits can therefore only be acce- 

 lerated by such means as increase the elongation of the cells, 

 and cause weak cells to develop healthily. In horticultural 

 practice, therefore, repeated watering and moderate application 

 of liquid manure is resorted to. 



The effectiveness of this procedure seems to be greater the 

 more the organ which develops into the fruit resembles a 

 vegetative axis. Liquid manure (in small quantities), or 

 water alone, prove therefore especially effective in the swelling 

 of apples and pears, figs, pine-apples, and strawberries. The 

 apple may be looked upon as a cup-shaped apex of a stem, 

 in which the carpels are sunk. The succulent portion of the 

 pear or apple is, therefore, mainly an excessively succulent 

 cortical tissue, as can best be seen in those cases in which the 

 fruit is continued on one side down the fruit-stalk. In the 

 case of the strawberry, the succulent axis is not hollow, but 

 forms a conical protuberance, and in its development we may 

 sometimes see the bad effects of too copious a supply of water 

 or nutritive salts. Many flowers remain sterile, and the 

 smaller number produce enormous fruits, which often become 

 hollow at their centre. The elongation of the cells is so ex- 

 cessive that a considerable tension exists at the centre, and 

 the cells separate one from another, as is the case in other 

 axial structures under similar circumstances (turnips and 

 potatoes). 



In the case of stone-fruits, a judicious supply of water will 

 also aid in the swelling of the fruits, but here considerably more 

 care is needed in selecting the proper time for such operations, 

 as otherwise the fruits are liable to be thrown off. Especially 

 in the case of peaches, apricots, and plums it seems desirable 

 to abstain from the application of liquid manure or from 



