HYBRIDISM 225 



another and distinct species, than by their own pollen ; 

 and all the individuals of nearly all the species of Hip- 

 peastrum seem to be in this predicament. For these 

 plants have been found to yield seed to the pollen of a 

 distinct species, though quite sterile with their own 

 pollen, notwithstanding that their own pollen was 

 found to be perfectly good, for it fertilised distinct 

 species. So that certain individual plants and all the 

 individuals of certain species can actually be hybridised 

 much more readily than they can be self-fertilised ! 

 For instance, a bulb of Hippeastrum aulicum produced 

 four flowers ; three were fertilised by Herbert with 

 their own pollen, and the fourth was subsequently 

 fertilised by the pollen of a compound hybrid descended 

 from three other and distinct species : the result was 

 that ' the ovaries of the three first flowers soon ceased 

 to grow, and after a few days perished entirely, whereas 

 the pod impregnated by the pollen of the hybrid made 

 vigorous growth and rapid progress to maturity, and 

 bore good seed, which vegetated freely.' In a letter 

 to me, in 1839, Mr. Herbert told me that he had then 

 tried the experiment during five years, and he con- 

 tinued to try it during several subsequent years, and 

 always with the same result. This result has, also, 

 been confirmed by other observers in the case of Hip- 

 peastrum with its sub-genera, and in the case of some 

 other genera, as Lobelia, Passiflora, and Verbascum. 

 Although the plants in these experiments appeared 

 perfectly healthy, and although both the ovules and 

 pollen of the same flower were perfectly good with 

 respect to other species, yet as they were functionally 

 imperfect in their mutual self-action, we must infer 

 that the plants were in an unnatural state. Neverthe- 

 less these facts show on ^hat slight and mysterious 

 causes the lesser or greater fertility of species when 

 crossed, in comparison with the -*ame species when self- 

 fertilised, sometimes depends. 



The practical experiments of horticulturists, though 

 not made with scientific precision, aeserve some notice. 

 It is notorious in how complicated a manner the species 



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