FRUIT. 



87 



149i There are cases in which suppression of ovules causes a 

 variation in the fruit, from what might be expected from an 

 examination of the ovary in its early stage. If an ovary of the 

 Chestnut be examined before or soon after impregnation, it will 

 be found to contain fourteen ovules in seven cells ; but in the 

 progress of development it becomes one-celled, and thirteen of 

 the ovules are obliterated. The ovary of the Oak is originally 

 three-celled, with six ovules; but when perfected it is one- 

 celled and one-seeded. There are many cases of this kind. 

 The reverse of this takes place in some cases, which would be 

 inexplicable were not the ovaries examined in their earliest 

 state. A one-celled ovary becomes a two or more celled fruit: 

 in the Cruciferae by the enlargement of the placenta ; in the 

 Astragalus by the expansion of the suture ; in other cases by 

 the dilations of the lining of the pericarps, which form horizon- 

 tal dissepiments. The Pomegranate presents a remarkable 

 variation from the true type. 



150. When the fruit arrives at maturity, the j^ericarp either 

 bursts or it remains closed ; if the latter, it is said to be inde- 

 hiscent, as in the apple, hazel-nut, &c. If it bursts, it is said to 

 be dehiscent, and it follows invariably the same course in the 

 same species; hence it is important to notice the varieties. In 

 some cases the dehiscence takes place by dividing the dissepi- 

 ments, that is, the carpels separate into their original leaves, as 

 in the Delphinium, and this is called septicidal dehiscence. Fig. 

 140 represents this kind, in which a represents the axis, d the 



Fig. 140. 



Fig. 141. 



Fig. 142. 



dissepiment, and v the valves. In other cases the dissepiments 

 are attached to the middle of the valves, and the dehiscence in 

 such cases, no doubt, takes place at the midrib of the leaves 

 that form the carpels. This is called loculicidal dehiscence, as 



149. How many ovules in the chestnut? How many perfected ? How 

 in the oak? When does the reverse take place?— 150. When is the fruit 

 said to be indehiscent? When dehiscent ? When is the dehiscence sep- 

 ticidal? When loculicidal? 



