SELECTION AND HYBRIDIZATION AMONG GRAPES. 



161 



ciples, as illustrated among the species of Primus, will apply quite as well in 

 any genus of plants having several species, as with Vitis), it is very essen- 

 tial to employ some rapidly accumulative methods which will bring together 

 in harmony and stableness the information sought. 



The process might still further be speeded, probably, by uniting in it 

 budding and grafting, which Professor Lucien Daniel of France claims will, 

 in many cases alone, produce true hybrids— as between tomatoes and potatoes 

 —among the plants grown from the seeds of the graft. Professor Daniel 

 mentions many examples of such hybrids in his writings about his work along 

 this line. I have never experimented any in this direction, and hence cannot 

 say how it would affect in combination with cross-pollination. I would 

 expect less stability in such hybrids, if we may properly term them such, 

 than those produced in cross-pollination.* 



I have conjectured sometimes whether or not it is possible for double 

 hybridization to take place in an ovule in a single operation by, at the same 

 moment, having a spermatozoid from each of two or more species to enter 

 the ovule egg-cell and fuse together with the protoplasm of the egg nucleus, 

 thus combining the blood of three or more species all at once. As the blood 

 of the several species can be eventually intermingled in one individual, by 

 successive crossings, there would seem no physiological reason why not all 

 at once, by applying mixed pollen to the stigma. But so far as the most 

 painstaking microscopic scrutiny among the few species of plants examined 

 reveals the process of fecundation by pollination, only one male nucleus has 

 ever been found to reach and fuse with the female nucleus, although several 

 spermatozoids have been observed lodged against the egg-cell wall of the 

 ovule, and a number of pollen tubes containing spermatids have been seen 

 at the same time bending into the archegonal chamber in the apex of the 

 lirothallus of the ovule.t It seems probable that the male and female nuclei 

 are minute polarized protoplasmic masses. The germinal nuclei may be 

 drawn to each other in a similar way that magnets attract each other.J 



The first spermatozoid to bore through the egg-cell wall by aid of its 

 spiral ciliary band is at once focused in the magnetic pole of the female 

 nucleus, which is much larger than the male nucleus, and drawn into it and 

 fused together. The female nucleus seems incapable of focalizing on or at- 

 tracting more than one male nucleus. They (the male and female nuclei) 

 appear to have passed the stage of spermatozoids instantly at moment of 



*See also Mr. A. Juric, in Revue des Hylirides Franco- Americains ou I'lsabelle de 

 I'oligny Ilybride de Greffe. 



til. J. Webber, in Bulletin Xo. 2, Bureau of Plant Industry, Dep. Agr. This 

 treats of fecundation in Zamia, but by the laws of comparative physiology we infer that 

 the process is similar in Vitis, in which the process has never been observed. The 

 flowers are too small, probably, even for the microscopic eye to observe it. 



JThe Blepheroplasts, or specialized centrosomes, similarly to the rays of a magnet, 

 curving back around and toward the central line of the central cell of the pollen tube, 

 strongly suggest magnetic force, or a very near relative, controlling the life movements 

 of the spermatid in the central cell, causing it to divide. But the formation of the 

 ciliary band and the swimming in the cytoplasm by means of the cilia, and the subse- 

 quent boring of the spermatozoid into the egg-cell, by means if its gimlet-like cone, 

 suggests more than mere blind magnetic force. It seems to be more akin to intelligent 

 or conscious pairing. 



