ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 177 



Jalapa and M. longiflora — for the purpose of determining the questions 

 of the relationship between the number of ovules actually impregnated 

 and the number of pollen-grains applied to the stigma, and between the 

 character of the seeds and seedlings and the number of pollen-grains 

 made use of. The results are in favour of the advantage given by 

 the application to the stigma of a large quantity of pollen. It was 

 found that in ilf. Jalapa there is only about one functional to four 

 functionless pollen-grains ; and that out of three ovules only two are 

 functional. In M. longiflora there was one functional to about three 

 functionless pollen-grains, and about an equal number of functional and 

 functionless ovules. If the stigma is pollinated by a large quantity of 

 pollen, the progeny is stronger (i.e. heavier), from the co-operation of 

 functional pollen-grains with one another. The quicker the pollen- 

 grain makes its way through the style, the stronger are the resulting 

 seeds and seedlings. 



Cross-Pollination and Self-Pollination. — In the hermaphrodite 

 flowers of the horse-chestnut, Prof. L. Macchiati * points out that the 

 change in the colour of the patches on the petals, from yellow to red, 

 corresponds to the change in the sexual condition of the proterogynous 

 flowers, and contributes to the efficiency of cross-pollination. The 

 flowers are nectariferous, and are visited by numerous Hymenoptera 

 of the class Apidee, which visit them first for their honey only, then 

 for both the honey and the pollen, and finally for the pollen only. 



In Hsemanthus tigrinus (Amaryllideae), (see p. 179), the flowers are, 

 according to Prof. F. Hildebrand,f capable of both self-pollination and 

 ci oss-pollination, the latter being apparently effected by honey-birds. 

 Experiments in artificial pollination indicated a distinct advantage in 

 favour of cross-pollination. 



The cultivated species of Chrysanthemum belonging to the species 

 C. indicum and C. sinense, are, according to R. Gerard,! proterandrous 

 and cross-pollinated. Artificial pollination is likely to prove of great 

 value in the production of new and superior varieties. 



Unequal Results of Hybridisation. § — Hugo de Vries adopts Mil- 

 lardet's term pseudo-hybrid || for those products of hybridisation which 

 do not present a combination of the characters of the two parents, the 

 crossing itself being termed anisogonous ; while those products which 

 exhibit a symmetrical splitting in the formation of their sexual organs 

 are true hybrids, and the process of crossing is isogonous. The observa- 

 tions were chiefly made on different species of (Enothera, in which genus 

 a much greater variety in the results of hybridisation was observed than 

 in most others, The first generation is sometimes uniform ; sometimes 

 it presents two or more distinct forms. The hybrids of this generation 

 usually produce, as the result of self-pollination, only one form of seed ; 

 but there are some in which the splitting of characters is displayed. 

 These do not then split into equal, but into unequal portions. 



* Bull. Soc. Bot. Ital., 1900, pp. 245-54. 

 t Ber. Deutsch. Bot. Ges., xviii. (1900) pp. 374-5. 

 t See Bull. Soc. Bot. France, xlvii. (1900) p. 371. 



§ Ber. Deutsch. Bot. Ges., xviii. (1900) pp. 435-43. Cf. this Journal, 1900, 

 pp. 484, 609. || Cf. this Journal, 1895, p. 451. 



April 17 th, 1901 N . 



