OBSERVATIONS UPOX MULING AMONG PLANTS. 



161 



of necrosis caused by the strange pollen proceeding from the 

 stigma to the ovules, for which we see little ground. 



After the fall of the blossom, the capsule often remains sta- 

 tionary, though there was every reason to suppose that impreg- 

 nation had taken place; and occasionally after the fruit is half 

 grown no further progress is made. Those capsules which arrive 

 at maturity acquire that condition in the same time as after natural 

 impregnation, even though the periods of maturation be different 

 in the two hybridizing species. The slow process of fecundation 

 is, however, compensated afterwards, and the time of maturity 

 proper to the matrix is preserved. In plants of warm climates, 

 indeed, a supposed difference exists, which may depend upon 

 depressed vital energies, as is certainly the case with the imper- 

 fect ripening of hybrid seeds late in autumn, when natural seeds 

 arrive at perfection. The outer aspect of the hybrid seeds is 

 indeed the same, and their embryo is more or less formed in 

 many cases, but they do not germinate. 



The time when impregnation will take place is comprised 

 within certain limits, varying with the particular species. Very 

 early experiments in hybrid fecundation before the expansion 

 of the blossom seldom succeed, and no impregnation will take 

 place with strange pollen when the stigma has arrived at such a 

 state that its own pollen is not able to fecundate the whole 

 ovary. In any case, however, there is no difference in the 

 hybrid types resulting from the experiment. 



When the stigma is dusted at the same time, or within certain 

 limits, with its own pollen in sufficient quantity, and that of 

 some other species, the latter is wholly inert, and the result is 

 plants not differing in any respect from the matrix ; nor is the 

 effect different if a division or portion of the stigma be dusted 

 with either pollen separately, precaution being taken that there 

 shall be no possibility of admixture. The elective affinity for 

 the natural pollen makes the other completely negative. 



The result is perfectly analogous when more than one kind of 

 strange pollen is applied, the native pollen being completely 

 excluded. One typical form alone results — the effect of the im- 

 pregnation of that pollen for which the stigma has the greater 

 elective affinity. Mr. Herbert produced from the admixture of 

 twelve different kinds of pollen merely one hybrid. In such cases 

 the number of perfect seeds is generally small, which is not sur- 

 prising under circumstances so thoroughly unnatural. The 

 author relates, however, a very curious exceptional instance. A 

 plant of Lychnis diurna was dusted with the pollen of Silene 

 noctiflora. Twelve capsules, of different degrees of perfection, 

 were set, which yielded from 20 to 80 seeds. The plants 

 produced by them were, with two exceptions, true L. diurna ; 



vol. v. 



