112 PROPAGATION OF PLANTS. 



the pistils in the center of the flower are the last to be 

 effected by cultivation, and often remain in a condition 

 to perform their natural functions long after the stamens 

 have changed to petals, and with a little assistance, to 

 prevent smothering the stigma, may be readily fertilized 

 artifically, and fertile seeds produced from quite double 

 flowers. There is, however, a limit to all operations of 

 this kind, as well as to our knowledge of vegetable struc- 

 tures, as, for instance, we occasionally find plants which 

 appear to have perfect sexual organs, and yet they resist 

 all effort? to make them fruitful, but why this is so we 

 are unable to determine. 



LIMITS OF CROSS-FERTILIZATION. The limits of 

 artificial fertilization of plants have never been deter- 

 mined, and they only can be through the aid of innumer- 

 able and oft-repeated experiments, and if we could decide 

 what is possible with plants, as they exist at this time, 

 new forms must necessarily appear as the result of artifi- 

 cial intermingling of species, thereby opening ne\v and 

 at present unknown fields for experiments and investiga- 

 tions. In the ever-changing phases of plant life, who 

 can say that the impossible of to-day will not be possible 

 to-morrow or a few years hence ? 



Under ordinary circumstances, xarieties of a species 

 may be cross-fertilized far more readily than species can 

 be hybridized. The distinction between the offspring of 

 species, and varieties is not so generally recognized as it 

 should be among cultivators of plants. Correctly speak- 

 ing, a li^brid is the offspring of two species. For 

 instance, if we should take the native Apple of Europe 

 (Pints Malus), which is the parent of nearly all of our 

 cultivated varieties, and the American Crab Apple (P, 

 coronaria), and by fertilizing the flo\vers of one species 

 with pollen from the other, produce a plant with the 

 characteristics of both combined, we would then have a 

 proper or true hybrid. But if we fertilize the flowers of 



