MATURATION OF THE PERICAP. 269 



process of fertilization should be complete. In speaking of seedless 

 Oranges, Dr. Bullar states that the thinness of the rind of a St. Michael 

 Orange, and its freedom from pips, depend on the age of the tree. 

 The young trees, when in full vigour, bear fruit with a thick pulpy 

 rind and abundance of seeds ; but, as the vigour of the plant declines, 

 the peel becomes thinner, and the seeds gradually diminish in number, 

 till they disappear altogether. 



562. While the fruit enlarges, the sap is drawn towards it, and a great 

 exhaustion of the juices of the plant takes place. In Annuals, this ex- 

 haustion is such as to destroy the plants; but if they are prevented from 

 bearing fruit, they may be made to live for two or more years. Peren- 

 nials, by acquiring increased vigour, are able better to bear the demand 

 made upon them during fruiting. If large and highly-flavoured fruit 

 is desired, it i^f importance to allow an accumulation of sap to take 

 place before the plant flowers. When a very young plant is permitted 

 to do so, it seldom brings fruit to perfection. When a plant produces 

 fruit in very large quantities, gardeners are in the habit of thinning it 

 early, in order that there may be an increased supply of sap to that 

 which remains. In this way, Peaches, Nectarines, Apricots, &c., are 

 rendered larger and better flavoured. When the fruiting is checked 

 for one season, there is an accumulation of nutritive matter, which 

 has a beneficial effect on the subsequent crop. 



563. The pericarp is at first of a green colour, and performs the 

 same functions as the other green parts of plants, decomposing car- 

 bonic acid under the agency of light, and liberating oxygen. As it 

 advances to maturity, it either becomes dry or succulent. In the for- 

 mer case, it changes into a brown or a white colour and has a quantity 

 of ligneous matter deposited in its substance, so as to acquire some- 

 times great hardness ; in the latter, it becomes fleshy in its texture, 

 and assumes various bright tints, as red, yellow, &c. In fleshy fruits 

 however, there is frequently a deposition of ligneous cells in the endo- 

 carp, forming the stone of the fruit ; and even in the substance of the 

 pulpy matter or sarcocarp, there are found isolated cells of a similar 

 nature, as in some varieties of Pear, where they cause a peculiar 

 grittiness. The contents of the cells near the circumference of succu- 

 lent fruits are thickened by exhalation, and a process of endosmose 

 goes on, by which the thiner contents of the inner cells pass out- 

 wards, and thus cause swelling of the fruit. As the fruit advances to 

 maturity, however, this exhalation diminishes, the water becoming 

 free, and entering into new combinations. In all pulpy fruits which 

 are not green, there are changes going on by which carbon is separ- 

 ated in combination with oxygen. 



564. Dry fruits may remain attached to the tree for some tune 

 before they are fully ripe, and ultimately separate by disarticulation. 

 Occasionally, when the pericarp is thick, it separates in layers like 



