M. Cli. Naiulin on Uyhridity in Plants. 221 



still retain all their value, the fact of the sterility of hybrids 

 being absolute in some cases, but only partial in otliers. 

 These two facts, since so frequently confirmed, cannot now 

 be disputed. In a former paper I gave some examples which 

 serve to illustrate them. 



We have seen Nicotiana-californico-rustica, N. glu~ 

 tinoso-macrophylla, N. glutinoso-cmgustifolio - macropJii/Ua, 

 Digitalis luteo-purpurea and Bibes Gorclonianum, sterile 

 both by the stamens and ovary — the former being totally 

 destitute of pollen well formed, and the latter incapable of 

 impregnation by the pollen of the parent plants. But as 

 the pistil does not in every case present any appreciable de- 

 formity, it is natural to seek in the ovule itself the true cause 

 of this inaptitude to receive impregnation. 



It has been fully proved by many cases of hybridity, in 

 which, in the same ovary one portion of the ovules resists im- 

 pregnation, whilst the other becomes converted into embry- 

 onic seeds capable of germinating — that this defectiveness 

 exists in the ovule, and not in the more exterior parts of 

 the pistil. 



We have seen this in the three hybrid generations of 

 Luff a acutangulo-cylindrica, also in Liffa amaro-cylindrica^ 

 Gucumis Meloni- trig onus, Nicotiana rustico-paniculata, and 

 paniculato-rustica, &c. Ciicumis myriocarpo-Figarei is a not 

 less convincing proof, since among 100 fruits which were 

 developed and ripened under the influence of pollen derived 

 from the maternal species, 19 at least were destitute of 

 seeds, and each fruit, among the small number which con- 

 tained any, only yielded one seed. I might mention, in 

 support of this fact, the example of Mirahilis longifloro- 

 Jalapa^ though in this case the ovary is uniovular. The 

 stigmas of this hybrid were all equally developed, and in 

 this respect not inferior to those of the parent species ; yet 

 eleven attempts to impregnate it with the pollen of Mira- 

 hilis longiflora were made without effect, and even ten were 

 necessary with that of M. Jalapa to determine the increase 

 of a single ovule. In the Luffa hybrids just mentioned, 

 and also in the case of Gucumis Meloni-trigonus, however 

 poor the pollen might have been which was employed to 

 fertilise their ovaries, it is beyond doubt that the number of 



NEW SERIES. VOL. XIX, NO. II. APRIL 1864. 2 F 



