12 



ON HYBRIDIZATION AMONGST VEGETABLES. 



It appears that if two stigma-bearing lobes of a triple or 

 even tripartible style are cut off, the whole germen may be 

 fertilized by the one left. In such cases, therefore, the pollen 

 tubes from one lobe must be able to penetrate all the cells of the 

 germen. In cases such as I have seen, where both natural and 

 hybrid seeds have been produced in one capsule, I cannot state 

 whether the two sorts of pollen acted through the same or dif- 

 ferent lobes. I have in no instance succeeded in obtaining any 

 multiplicate cross by blending the pollen of two or more kinds 

 intimately before their application. Mr. Knight thought he had 

 given at the same time the curl of one cabbage and the red colour 

 of another to a third variety. My invariable failure in such 

 attempts induces me to think his recollection was inaccurate, if 

 he meant that he had done so at one fructification. He might 

 easily have obtained the twofold features by two successive crosses, 

 but I believe not in one generation by simultaneous application 

 of different pollens : for I do not think that two grains even of 

 the same pollen can get effectual access to the foramen of one 

 and the same ovule. I now understand, nearly at least to my 

 own satisfaction, in what manner the pollen of Rhododendron may 

 in the fertilization of the ovules supersede the pollen of Azalea 

 previously applied ; because I do not believe that they are always 

 fertilized so soon as has been usually supposed. The stimulus 

 may have been given to the germ or outer coat of the seed-vessel, 

 and yet the fertilization may not have reached the ovule, and the 

 operation which produces a living embryo may remain suspended 

 till a change of weather and a moist atmosphere afford a supply 

 of carbon, or whatever is needful thereto ; and therefore that 

 pollen which has perfect affinity to the plant may develop itself 

 effectually at a later period on a change in the state of the atmos- 

 phere ; but, when the pollen has once reached and stimulated the 

 foramen, further access will be assuredly denied. I have repeatedly 

 observed in dry seasons the pollen of Rhododendron very parched 

 and seemingly deficient, the stigmas dry, and the germens remain- 

 ing for weeks nearly stationary after flowering, as if no seed 

 would be produced ; but, upon a change of weather inducing 

 moisture, universal fertility of the pods soon became apparent. 

 I suspect that in such cases the fertilization has remained incom- 

 plete from want of the food necessary to the elongation of the 

 tubes. If such views have any foundation in truth, it is possible 

 that, in addition to mere water, a supply of the chemical ingre- 

 dients which are the food of plants to the style may facilitate 

 difficult impregnations. It is certainly desirable, where dry pollen 

 is to be tried, to moisten the stigma to which it is about to be 

 applied. 



Having made these preliminary observations, I will try to re- 



