ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 71 



actual fusion betwoeu the two nuclei. No individualised centrosomes 

 or centrospheres have been found to occur in connection with the first 

 division following fertilisation. The number of chromosomes in the 

 nucleus of the ventral canal-cell, in the nuclei of the sheath-cells, and in 

 the nucleus of the oosphere, has been found to be twelve, while the 

 mitotic figure in the first division following fertilisation, shows twenty- 

 four chromatic segments. 



A good bibliography is appended to the paper. 



Formation of the Ovule and Embryo-sac in the Araliaceae.* — 

 L. Ducamp has followed these out in several genera of this order, the 

 following being among the more important results obtained. 



The ovular protrusions are formed in pairs for each loculus on the 

 margin of the carpel ; one of the two grows upwards and aborts ; the 

 other descends into the cavity of the ovary and occupies a lateral posi- 

 tion. The nucellus is developed from three or four hypodermal cells. 

 One of these, the privileged cell, gives birth, after several divisions, to 

 the primordial mother-cell of the embryo-sac. The fusion of the polar 

 nuclei in the embryo-sac takes place before the flower opens. When the 

 embryo-sac is developed, the nucellus has become reduced to a small 

 column of four or five filaments of cells ; the result of a diastatic 

 action in the cells before the formation of the embryo-sac. A similar 

 change appears to take place in the integument, an inner zone of which 

 contributes to the nutrition of the embryo-sac. At maturity the endo- 

 sperm is covered by a membrane-like layer representing the inner zone 

 of the integument, a horny layer with masses of calcium oxalate derived 

 from the outer zone, and the external integument. 



Embryo of Hedera.j — L. Ducamp gives further details of the de- 

 velopment of the embryo in the ivy, which presents no important 

 departure from the normal in its early stages. The first division of 

 the impregnated cell is transverse ; the upper segment giving birth to 

 the embryo, the lower to the suspensor. In the formation of the root- 

 cone, the central cylinder is entirely independent of the suspensor ; the 

 growth downwards of the latter gives rise to the cap ; while the upper 

 elements of the cap are formed by the base of the embryonal epiderm. 



Cross-Pollination and Self-Pollination.— -Dr. D. Clos J describes the 

 phenomena connected with the flowering and pollination of several 

 species grown in the botanic garden at Toulouse, including Cobsea 

 scandens, which he regards as self-pollinated. 



A. Mainardi § regards the poppy (Papaver Bliceas) as probably 

 originally anemophilous. The dark spots at the base of the petals now 

 serve to attract species of Xylocopa ; these press out the pollen on to the 

 hairs which cover the abdomen ; then carry it away, and deposit it on 

 the stigma of another flower. 



Change of Sexuality in Plants. || — A. Gallardo has experimented on 

 the production of male and female flowers in successive generations of a 



* Comptes Rendus, cxxxiii. (1901) pp. 753-6. t Tom. cit., pp. 651-3. 



X Bull. Acad. Sci. Toulouse, 1900, pp. 219-31. 

 § Nuov. Giorn. Bot. Ital., viii. (1901) pp. 49-63. 



|| Cornni. d. Mus. Nat. Buenos Aires, i. (1901) pp. 273-91. See Bot. Centralbl., 

 Ixxsvii. (1901) p. 434. 



