Il6 HYBRIDISING AND CROSS-BREEDING. 



reaches the nucleus and embryo-sac. ... As soon as the 

 contact of the pollen-tube and embryo-sac is effected, a kind 

 of osmotic action between the contents of the two takes place, 

 the result of which is the development of one, or rarely two, of 

 the germinal vesicles into embryos." 



All the actual work of fertilisation is carried forward by the 

 organs and tissues of the female plant and the growth of the 

 male pollen ; and the work of the hybridiser is to bring these 

 parts into juxtaposition at the most opportune moment i.e., 

 when both are in vigorous perfection and to see that the seed- 

 bearing plant is well nourished at the root, until the seed is per- 

 fectly ripe. Dr Denny, in his paper read before the Birmingham 

 Congress (see Gard. Chron., 1872, p. 872, 904) on "The Rela- 

 tive Influence of Parentage in Flowering-plants," remarks : " The 

 visible effects of impregnation are frequently manifested with 

 a rapidity almost equalling that of an electrical phenomenon. 

 I have observed the petals of the Pelargonium, which before 

 impregnation were quite firm, to fall within a few seconds of 

 the application of the pollen to the stigma a result due, I 

 conclude, either to the immediate diversion of nourishment 

 from the then superfluous part of the flower to the organs of 

 generation, or to the existence in the vegetable kingdom of a 

 power analogous to the nervous in the animal, but of which we 

 are -as yet in total ignorance." As a rule, hybridisers trust to 

 one application of pollen ; but it is advisable to experiment by 

 applying the pollen to the stigma at different times, so long 

 as it remains in a receptive condition. The stigmas of some 

 flowers, as Poppies, Lilies, Nymphaea, and Gardenias, seem to 

 require a large quantity of pollen to fertilise them properly ; 

 while in other flowers the least quantity a few grains, in fact 

 once applied seem amply sufficient. Some guide to the 

 amount of pollen required may be obtained by noting the 

 number of seeds produced in the capsules, and by noting the 

 profusion of pollen naturally supplied (as in Poppies) when 

 the number of ovules to be fed is large. If the stigma appears 

 to absorb the pollen readily, and remains moist or receptive as 

 if requiring more, apply pollen again and again at short inter- 

 vals. On the other hand, it is possible that in some cases the 

 application of too much pollen may lead to the disorganisation 

 of the stigma, and thus defeat the object one has in view : and 

 as the elongation of the pollen-tubes is actually carried on by 

 the growth or addition of cells to their extremities, and as it 

 is now pretty certain that they are sustained and fed by the 

 juices which they absorb from the moist cellular tissues of the 

 style, it follows that if we apply too many pollen-grains to the 



