126 HYBRIDISING AND CROSS-BREEDING. 



into purple or brown when it stretches into the green parts of 

 the leaf. 



Fixation of Varieties and Races* The "fixing" of any 

 variety by artificial means, such as suitable culture, careful 

 selection of seed, &c., is easy to the intelligent cultivator ; and 

 whenever a " break " or " sport," or cross-bred seedling of a 

 desirable character, or exhibiting a tendency towards any stand- 

 ard of excellence, makes its appearance, other excellences 

 soon follow under the fostering care of the horticulturist. 



"The florist, to 'fix' the form, carefully isolates the plant; 

 but in the wild state a distinct sport or seminal form has no 

 chance, the bee from the neighbouring flower of course fertilis- 

 ing it with the pollen from any of the other forms. If there 

 were no bees, no agency whatever for cross-fertilisation, noth- 

 ing but the plant's own pollen to depend on, there would 

 undoubtedly be anomalous races, which, again, by natural 

 evolution at times changing, would produce other races ; and 

 in time the difference might be so great as to be even thought 

 generic. But we see that, by the agency of the humble-bee, 

 the progress of the newly-evolved form is checked. The pollen 

 of the original form is again introduced to the offspring, and it 

 is brought back at least half a degree to its starting-point. 

 Insects, in their fertilising agencies, are not always abettors, 

 but rather at times conservators of advancing evolution. "- 

 (Meehan.) 



When the florist cross-fertilises two pure species, the offspring 

 which result from the union possess a general family likeness, 

 although the elementary characteristics of the two species may 

 be united in different proportions in the different individual 

 seedlings. Races thus obtained are, however, far from con- 

 stant in character as a rule, unless again crossed with a third 

 species, or with a distinct variety of a third species, which, I 

 have repeatedly observed, has the effect of fixing the characters 

 of seedling races; but why this is so, I cannot just now 

 explain. Careful selection and good culture (i.e., a system of 

 culture which most favours the development of the character- 

 istics we wish the seedlings to assume, and which least favours 

 those characteristics we do not require) are the most power- 

 ful aids in fixing or rendering permanent races and varieties. 

 Plants, like animals, adapt themselves within certain limits to 

 the soil and locality or climate in which they may be placed ; 



* Those interested in this phase of our subject will find much useful in- 

 formation in a work by M. Carriere, entitled ' Production et Fixation des 

 Varieties dans les Vegetaux. ' 



