ADVANTAGES OF HYBRIDIZATION. 167 



where between those of the parent-forms has exceptions. 

 On the one hand, on account of individual variation, some 

 characters may pass beyond these limits, especially when the 

 cross is between varieties of the same species. On the other 

 hand, in species-hybrids there is a deviation from the rule, 

 owing to the fact that crosses between nearly related species 

 are weakened in the essential organs (stamens and pistil), but 

 in their organs of vegetation (root, stem, and leaf) are more 

 luxuriant. Hybrids of remote species develop very imper- 

 fectly in all their parts, and, from lack of energy in the vital 

 processes, soon perish. 



According to Nageli, species-hybrids often exhibit some 

 very remarkable characters. Their growth and development 

 may be so much modified, that they exceed their parents in 

 size, and excel them in vigor. Their leaves may be larger 

 and more numerous, the root-system much richer. Their 

 buds may be larger and stronger, and the facility with winch 

 bud propagation can be accomplished be increased. They 

 have frequently a longer lease of life ; annuals sometimes 

 giving rise to biennials or to perennials. They are generally 

 more hardy, and they bear exposure to cold and to rough 

 weather somewhat better. They often bloom earlier, have 

 flowers of richer color, of greater fragrance, and there is a 

 marked tendency towards the production of double blossoms. 

 On the other hand, the stamens and pistil are almost always 

 proportionally weak. 



9. In general, hybrids vary less in the first generation in 

 proportion to the remoteness of the parent-forms. Species- 

 hybrids vary less than variety-hybrids; the former being 

 characterized by uniformity, the latter by diversity. If, how- 

 ever, the hybrid is self-fertilized, the variability is greatly 

 increased, sometimes in an extraordinary manner when it did 

 not vary in the first generation. 



In short, as has been well shown by Naudin^ and by others, 

 when a hybrid is produced, we have secured a plant which 

 has a tendency to vary ; and of this tendency cultivators can 

 make great use. A hybrid, or its descendants at least, can 

 be said to drift ; and a skilled hand can take advantage of 

 this drifting, and to a great extent, by selection, direct the 

 subsequent course. Here is one of the great advantages of 



1 See note C at the end of the lecture. 



