OBSERVATIONS UPON MULING AMONG PLANTS. 



159 



a longer process, and therefore subject to more impediments ; 

 while all ungenial influences in normal fecundation acquire a 

 greater force. The results too, under precisely similar circum- 

 stances, are extremely different, whether as to the more or less 

 complete setting of the fruit, or the number or perfection of the 

 seeds produced ; far more so than might be expected from the 

 results of artificial impregnation of stigmas with their own pollen ; 

 and still more from the solitary instances in which experiments 

 have succeeded between different plants, where numberless 

 attempts have failed, as in the case of Lychnis dinrna $ and 

 Flos Cuculi $ . The difficulty seems to exist to a greater 

 degree in the matrix than in the strange pollen ; for even though 

 the protrusion of pollen tubes be caused by the moisture of the 

 stigma, the necessary penetration does not take place. The same 

 attraction does not exist which is consequent on the application 

 of its own pollen. 



In most cases the preference for its own pollen is so strong, 

 that no hybridization will succeed unless it be completely ex- 

 cluded, even in the most minute quantity. But even where this 

 condition is secured, much depends on propitious external in- 

 fluences. A certain degree of warmth is necessary, spring and 

 autumn being far less eligible for hybrid fecundation than 

 summer : the most favourable time at all seasons is usually the 

 morning. Species, such as Dianthus chinensis and Nicotiana 

 rustica, which readily set their fruit in autumn even in cold 

 weather, and in which hybrid fecundation is easy in summer, 

 when hybridized late in the year produce in general no fruit, 

 the blossom falling off prematurely, or the fruit when present 

 being imperfect and sterile, or yielding very few good seeds. 

 Rain and moisture are prejudicial to natural, and much more 

 to hybrid fecundation, because the former often takes place in 

 closed flowers, but the latter in those only in which the female 

 organs are exposed. 



Hybrid fecundation is not only more difficult, but it is also 

 when successful less productive than that which is natural. 

 Mr. Herbert indeed assures us that he has obtained more plants 

 from Crinum capense, fertilized with the pollen of C. revolutvm, 

 than from the pure seeds. This may merely be exceptional ; but 

 it is to be observed that Gartner had very few opportunities of 

 studying the laws of hybridization in monocotyledons ; and we 

 cannot subscribe to the probability of Mr. Herbert making such 

 a mistake as confounding the fertility of a mule already pro- 

 duced with the original generation of the hybrid seeds from 

 which it sprang. Hybrid Daturce and many mule Pinks produce 

 capsules far richer in seeds than the pure species from which 

 they were produced. 



