HYBRIDS 127 



one parent may remain latent as with heterodynamic 

 hybrids, and these latent characteristics may appear 

 in later progeny. The term derivative hybrids is 

 applied to the progeny of hybrids crossed with hy- 

 brids. Hyb ids of any sort often show new pecu- 

 liarities which are not derived from either parent. 

 This may be exhibited in the time of bearing or the 

 kind of bearing, or in rapidity of growth, for 

 example. 



In cross pollination we have depended up to the 

 present time upon the stimulus of enzymes contained 

 in the flowers for promoting the union of gametes 

 (two sex elements joined to make a zygote or 

 germ). This, however, is a chemical process. If 

 parthenogens in lower animal life may be made by 

 artificial stimuli it is possible that the hybridizers of 

 to-morrow may find artificial stimuli which will en- 

 courage formation of a zygote between gametes of 

 species which at the present time do not unite to 

 form hybrids. One feels that to-day we are merely 

 upon the verge of horticultural knowledge which 

 will be revealed to the plant physiologists and horti- 

 culturists of to-morrow. 



Nature's purpose of sex union is apparently to 

 combine the characteristics of both parents, and this 

 tendency is so well marked that some species of 

 plants have actually protective apparatus to prevent 

 access of their own pollen to the female flowers of 

 the same plant. Remarkable nut trees, like other re- 

 markable fruit trees, represent variants from the 

 mean type and, following organic law in this respect, 



