ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 541 



winter ; in the spring abnormal flowers abounded. The author con- 

 siders that the great factor in the production of abnormal violet flowers 

 is connected with the existence of two classes of flowers, the large-petalled, 

 which usually fail to form fruit, and the cleistogamic, which are 

 productive. 



Sexuality in the Genus Ribes.* — Ed. de Jancewski finds as a result 

 of examination of the species of Riles occurring in South America, that 

 these are all practically dioecious, thus contrasting with the North 

 American species. Both stamens and pistil are present in all the 

 flowers, but on some plants the stamens, on others the pistil, show 

 various degrees of abortion. In several species the flowers are apparently 

 hermaphrodite, but the anthers in the fruit-producing flower contain in 

 place of functional pollen a mass of parenchyma-like cells, which are 

 apparently aborted pollen-mother-cells, while the ovules in the male 

 flowers are rudimentary. The Isthmus of Panama constitutes a natural 

 limit between species, w r hich, while closely allied and very near in all 

 other respects, differ in the incomplete development of the sexual organs 

 in the Southern species. 



Nutrition of the Egg- in Zamia.t — Isabel S. Smith describes the 

 mode of nutrition of the egg by jacket-cells in Zamia. The inner walls 

 of the jacket-cells are pierced by numerous pores of various sizes, through 

 which the protoplasm of the egg protrudes into the jacket-cells, forming 

 haustoria-like processes. After passing through the pits the ends of the 

 haustoria become distended so that the structure appears knob-shaped. 

 The haustorium behaves like a gland cell, during the period of accumu- 

 lation staining more and more deeply, then discharging, and during the 

 following period of exhaustion staining faintly until the active period 

 begins again. In no case was there any indication of the passage of 

 nuclei or nucleoli from the jacket-cells into the egg, and in no case was 

 a jacket-cell found without a nucleus. It often happens that the knob- 

 like ends of haustoria are cut longitudinally and then closely resemble 

 nuclei, and might be mistaken for nuclei passing bodily into the egg. 

 This may explain the passage of the nuclei described by Arnoldi in 

 Pinus, but not confirmed by subsequent investigators. No sieve-plates, 

 or similar structures, as described by Goroschankin in Ceratozamia, were 

 found in the present instance. 



Embryo-sac and Fertilisation 4n Aster.! — Marie Opperman has 

 investigated these stages in the life-history of several species of Aster. 

 The embryo-sac arises from the lowest cell of an axial row of four cells, 

 and the eight-nucleate sac is formed in the usual way. There is con- 

 siderable variation in the form of the embryo-sac, both in different 

 species and in the same species. Generally the polar nuclei fuse before 

 fertilisation, but may fuse after it. The endosperm nucleus is marked 

 out by its large size, almost spherical shape, its large nucleolus and its 

 position below and in contact with the oosphere. The antipodals show 

 a remarkable growth before the time of fertilisation, and persist till the 



* Bull. Internat. Acad. Sci. Cracow, 1903, No. 10 (1904) pp. 788-92 (7 figs, in text)- 

 t Bot. Gazette, xxxvii. (1904) pp. 346-52 (6 figs, in text). 

 X Tom. cit., pp. 3f>3-62 (2 pis.). 



