204 MISCELLANEOUS 0BJE0TI0N8 TO TBJB 



ably been gained through natural selection. No one until 

 lately would have imagined that in dimorphic and tri- 

 morphic plants the different lengths of the stamens and 

 pistils, and their arrangement, could have been of any 

 service, but now we know this to be the case. 



In certain whole groups of plants the ovules stand erect, 

 and in others they are suspended; and within the same 

 ovarium of some few plants, one ovule holds the former 

 and a second ovule the latter position. These positions 

 seem at first purely morphological, or of no physiological 

 signification; but Dr. Hooker informs me that within the 

 same ovarium, the upper ovules alone in some cases, and 

 in others the lower ones alone are fertilized; and he sug- 

 gests that this probably depends on the direction in which 

 the pollen-tubes enter the ovarium. If so, the position of 

 the ovules, even when one is erect and the other suspended 

 within the same ovarium, would follow the selection of any 

 slight deviations in position which favored their fertiliza- 

 tion, and the production of seed. 



Several plants belonging to distinct orders habitually 

 produce flowers of two kinds — the one open, of the ordi- 

 nary structure, the other closed and imperfect. These two 

 kinds of flowers sometimes differ wonderfully in structure, 

 yet may be seen to graduate into each other on the same 

 plant. The ordinary and open flowers can be intercrossed; 

 and the benefits which certainly are derived from this pro- 

 cess are thus secured. The closed and imperfect flowers 

 are, however, manifestly of high importance, as they yield 

 with the utmost safety a large stock of seed, with the ex- 

 penditure of wonderfully little pollen. The two kinds of 

 flowers often differ much, as just stated, in structure. The 

 petals in the imperfect flowers almost always consist of 

 mere rudiments, and the pollen-grains are reduced in 

 diameter. In Ononis columnae five of the alternate sta- 

 mens are rudimentary; and in some species of Viola three 

 stamens are in this state, two retaining their proper func- 

 tion, but being of very small size. In six out of thirty of 

 the closed flowers in an Indian violet (name unknown, for 

 the plants have never produced with me perfect flowers), 

 the sepals are reduced from the normal number of five to 

 three. In one section of the Malpighiaceae the closed 

 flowers, according to A. de Jussieu, are still further modi- 



