120 HYBRIDISING AND CROSS-BREEDING. 



resulting offspring are, as may be supposed, wanting in consti- 

 tutional vigour. As observed by De Candolle, the three 

 primary colours, red, blue, and yellow, are rarely found united 

 in the same species or even in the same genus ; and the same 

 chemical causes which affect colour may possibly be connected 

 with this interesting question of sexual or constitutional affinity, 

 since, as Gaertner observes, it is not governed by either sys- 

 tematic or morphological laws. Observing cultivators, and 

 especially hybridisers, may greatly facilitate the solution of this 

 problem by carefully recording the parentage of the hybrids 

 they raise. 



Balance of Sexual Power and Prepotence. I may here remark 

 that the late Dr Lindley believed that superfoetation was 

 possible, although not probable, unless the flowers were care- 

 fully emasculated, since, as a rule, pollen of the same species 

 is prepotent, though in one or two known instances, notably in 

 the case of some Passion-flowers, their own pollen is impotent, 

 while that from another plant of the same species or from 

 another species induces fertility. The late Dean Herbert, 

 writing upwards of thirty years ago, remarks : " In some genera 

 we find that all the species are capable of breeding together 

 and producing fertile offspring ; in Hippeastrum, that they even 

 prefer breeding with each other; in some genera, that many 

 species will cross together, and some have as yet refused to 

 cross ; in some, that the cross-bred plants are abundantly 

 fertile, in some obstinately sterile; in some, individuals capable 

 of fertilisation by the pollen of another, and not by its own ; in 

 some cases, that two individuals will breed freely with a third, 

 and not with each other." The sympathies of plants will re- 

 main a mystery to us until we estimate their sexual vigour and 

 its causes apart from mere vegetative growth, which is often 

 very deceptive ; indeed, as a rule, barren plants vegetate much 

 more vigorously than such as are fertile, and this is notably the 

 case with hybrids that are barren or do not produce fertile 

 seeds. It is a fact, but one too little appreciated, that fruit or 

 seeds are not beneficial to the plant as an individual, but rather 

 prejudicial, since many plants become starved to death annu- 

 ally by their fruit, which appropriates all the nourishment taken 

 up by the roots. As to the prepotence of the male or female 

 parent, the whole thing seems to hinge on perfect health and 

 constitutional vigour that is to say, if the male and female 

 parents are equal in constitutional energy and sexual vitality, 

 then the progeny will be intermediate between any two species. 

 But in the case of varieties there is the tendency to ancestral 

 reversion to overcome in addition, and it is well known that the 



