112 FRUITING. 



having a gland on each angle. To each gland there is attached 

 a pair of yellow bags containing the pollen, and called ^w/Ze/^ 

 masses. These do not open, and the stigma has no secreting 

 surface. In these circumstances, the impregnation of these 

 plants offered an important problem for solution. Ehrenberg 

 found that through one side, that next the stigma of these pol- 

 len manes, pollen tubes were emitted, and directly entered the 

 stigma, and made their way to the ovary, as in other cases, thus 

 showing the perfect agreement, in this case at least, with other 

 phanerogamous plants. It has also been proved more than 

 probable that similar arrangements accomplish the same end jn 

 Orchideae. In orthotropous plants, threads in some cases hang 

 down in the cavity of the ovary, through which the pollen can 

 pass into the foramen. In other cases, the conducting tissue 

 elongates so as to reach the foramen during the time of fertiliza- 

 tion. In Euphorbia, the apex of the nucleus is protruded far 

 beyond the foramen, so as to lie within a kind of hood-like ex- 

 pansion of the placenta. 



I 



Section 2. — Fruiting. 



200i By fruiting we understand the changes the ovarium 

 and its connected parts undergo in arriving at maturity. We 

 have already noticed the changes which take place in the con- 

 tents of the ovary. The changes of the other floral organs, in 

 many cases, are no less prompt and distinct. The floral en- 

 velopes soon wither, unless connected with the ovary ; the stamen 

 falls off", the pistil dries up or hardens when composed in part 

 of the axis of the plant, and all the energies of the plant seem 

 to be directed to the perfection of the fruit or ovary. That 

 these changes are effected by the act of fertilization, may be 

 made manifest by preventing the access of the pollen to the 

 pistil, and the parts will for a much longer time remain un- 

 changed. There seem to be two different courses taken in the 

 perfection of different fruits. In one, the ovaiy becomes dry, 

 hard, membraneous or woody, as in the Poppy, Cantua, &c 

 In others, the ovary becomes fleshy, affording various agreeablf 

 articles of food, as Apples, Pears, Peaches, Melons, (fee. Thi? 

 has been supposed tp depend upon the number of stomata or 

 the surface of the ovary. In the dry one, the stomata werf 

 suflScient to permit the evaporation of all the moisture, while ip 

 the fleshy comparatively little evaporation took place, from the 



200. What is fruiting ? How are the floral envelopes affected by fertil- 

 ization? How made manifest? What two courses taken in the perfec- 

 tion of fruit ? 



