320 MATURATION OF THE PEEICAEP. 



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 fuU 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 dis- 

 appear altogether. 



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. 

 Perennials, 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 is of importance to allow an aocumidation 

 of sap to take place before the plant flowers. The wood should be 

 well ripened. When a very young plant is permitted to bear fruit, it 

 seldom brings it to perfection. When a plant produces fruit in very 

 large quantity, gardeners are in the habit of thinning it early, in 

 order that there ipay be an increased supply of sap to that which 

 remains. In this way. Peaches, Nectarines, and Apricots, are ren- 

 dered 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. 



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

 functions as the other green parts of plants, decomposing carbonic 

 acid under the agency of light, and liberating oxygen. Saussure 

 found by experiments that all fruits in a green state perform this pro- 

 cess of deoxidation. As the pericarp advances to maturity, it either 

 becomes dry or succulent. In the former 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 sometimes great hardness, when it is 

 incapable of performing any active process of vegetable life ; in the 

 latter it becomes fleshy in its texture,, and assumes various bright 

 tints, as red, yellow, etc. In fleshy fruits, however, there is fre- 

 quently a deposition of ligneous cells in the endocarp, 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 con- 

 tents of the cells near the circumference of succulent fruits are thick- 

 ened by exhalation, and a process of endosmose goes on, by which the 

 thinner contents of the inner cells pass outwards, and thus cause 

 sweUing of the fruit. As the fruit advances to maturity, however, 

 this exhalation diminishes. In all pulpy fruits which are not green 

 there are changes going on by which carbon is separated in combina- 

 tion with oxygen. 



