664 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tricarpellary ovary become early aborted, while the single ovule of the 

 remaining locule develops normally. The embryo-sacs of the abortive 

 ovules develop, but undergo changes correlated with their loss of function. 

 The polar nuclei of the embryo-sacs of the functional ovule fuse before 

 flowering ; three antipodals are prominent, but soon disintegrate. The 

 nucellar tissue, small in amount, disappears as the embryo-sac develops. 

 The endosperm develops rapidly, and is surrounded by the integument ; 

 integumental cells infringing on the endosperm constitute a tapete which 

 does not disintegrate. 



Fertilisation of Salisburia.* — S. Ikeno supplements Hirase's ob- 

 servations on the mode of impregnation of Salisburia adiantifolia (Gingko 

 biloba). One only of the antherozoids from the pollen-tube is absorbed 

 into the oosphere, the other perishing. The process of development of 

 the nucleus of the oosphere is in complete accordance with that observed 

 in Cycas and Pinus. The two conjugating nuclei are very unequal in 

 size, the difference being even greater than has previously been observed 

 in Gymnosperms ; the female has quite ten times the volume of the male 

 nucleus. As in other Gymnosperms, the small male nucleus slowly 

 penetrates the female nucleus, the fusion of the substance of the two 

 nuclei taking place very gradually. 



Ovule and Embryo of Potamogeton.f — G. M. Holferty describes the 

 structure and development of the ovule and embryo in Potamogeton 

 natans. There is no wide departure from the normal. The embryo-sac 

 is much more deeply seated than in many other plants, occupying the 

 centre of the nucellus, and being surrounded on all sides by a mass of 

 tissue from 5—8 cells in depth. The archespore consists of a single 

 hypodermal cell, which divides into an outer or tapetal cell and an inner 

 cell, the primary sporogenous cell or megaspore. There appear to be 

 four potential megaspores. The antipodals are of short duration. The 

 polar nuclei do not meet in the centre of the sac, but always nearer the 

 antipodal end. The suspensor consists of a single cell, which is remark- 

 ably large and vesicular. 



Endotropic Course of the Pollen-tube.:}: — After a short resume of 

 recent observations on the chalazogamic mode of impregnation in Angio- 

 sperms, especially those on Alchemilla, Dr. B. Longo disputes the ex- 

 planation which has been given of chalazogamy, that it is due to the 

 incapacity of the pollen-tube to grow across a cavity. Experiments on 

 the artificial production of pollen-tubes induce him to believe that the 

 explanation must be sought in chemotactic phenomena ; — that the poro- 

 gamic or chalazogamic course of the pollen-tube is determined by the 

 presence of special chemotactic substances which are developed, in the 

 one case within the tissues, in the other case outside of them. 



Pollen-tube of Pinus.§ — Miss M. C. Ferguson has investigated the 

 development of the pollen-tube and the division of the generative 



• Ann. Sci. Nat. (Bot.), xiii. (1901) pp. 305-16 (2 pis.). Of. this Journal, 1896, 

 p. 328. 



t Bot. Gazette, xxxi. (1901) pp. 339-46 (2 pis. and 1 fig.). Cf, this Journal, 

 1898, p. 323. 



% Atti R, Accad. Liucei, x. 2* Sem. (1901) pp. 50-4. Cf. this Journal, ante, 

 pp. 431-3. § Ann. of Bot, xv. (1901) pp. 193-223 (3 pis.). 



