HYBRIDISING AND CROSS-BREEDING. 133 



ingredients are attracted by the pollen less readily and insuffi- 

 ciently, and by many of the grains not at all. 



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

 even tripartite style are cut off, the whole germen may be fer- 

 tilised 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 different 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 fertilisation of the ovules supersede the pollen of 

 Azalea previously applied ; because I do not believe that they 

 are always fertilised 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 fertilisation 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 atmosphere ; 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 remaining 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 fertilisation 

 has remained incomplete from want of the food necessary to 



* It is now known that it is quite possible for two pollen-tubes to enter 

 the apical aperture or foramen of the same ovule. 



