~>6 SUMMARY OF CUERENT RESEARCHES RELATING TO 



Fabci) by the extirpation of the flowers. He finds the result of the 

 castration to be invariably a much more luxuriant development of the 

 whole of the vegetative system, especially of the root-tubercles. The 

 castrated plant continues to develope after the period when normally 

 it would have ripened its seeds and then perished. The production of 

 fruits and of tubercles appears to be always in inverse proportion the 

 one to the other. The conclusion 6ecms inevitable that the purpose 

 of the tubercles is to provide a source of food-supply for the leaves, 

 and that the ploughing into the soil of the crop before the flowers are 

 developed must tend greatly to increase its productiveness. 



$. Physiology. 

 (1) Reproduction and Embryology. 



Sexual Reproduction. * — Prof. P. A. Dangeard proposes a new 

 classification of sexual phenomena, in accordance with the most recent 

 discoveries in this department of physiology. 



Wherever there are gametes, there is sexual reproduction, and 

 gametes are zoospores deprived of energy ; there are facultative gametes 

 which develope indifferently with or without previous conjugation ; and 

 a transition is thus established between sexual and non-sexual repro- 

 duction. The energy which incites the development of gametes is not 

 necessarily sexual ; when it is furnished by a physical or chemical 

 cause we have parthenogenesis, when by the action of one gamete on 

 another, we have sexual autophagy. This autophagy is of three kinds, 

 viz. : — (1) primitive autophagy or protogamy, in which the gametes 

 combine without fusion of the nuclei ; (2) ordinary autophagy or holo- 

 <jamy, where the nuclei fuse together as well as the cytoplasms ; (3) 

 reduced autophagy or merogamy, which does not require the participa- 

 tion of the whole of a second gamete, but only either of its cytoplasm 

 or of its nucleus. Among isogamous species, two cases are possible : — 

 the gametes may be impregnated by the cytoplasm of the second gamete 

 or by its nucleus. The second case is unknown; the first appears to 

 occur in Infusorians. In heterogamous species, merogamy includes 

 four distinct cases : — (1) The male gamete is impregnated by the cyto- 

 plasm of the female gamete, cytoplasmic androgamy ; (2) The male is 

 impregnated by the nucleus of the female gamete, nuclear androgamy ; 

 (3) The female gamete is impregnated by the cytoplasm of the male 

 gamete, cytoplasmic gynogamy ; (4) The female is impregnated by the 

 nucleus of the male gamete, nuclear gynogamy. Hertwig's, Boveri's, 

 and Delage's experiments are concerned with cytoplasmic androgamy ; 

 the partial impregnation of Boveri is a case of cytoplasmic gynogamy. 

 The author adopts Giard's term adelphophagy fur a union of gametes of 

 the same sex. 



In the view of the author, all the eight nuclei of the embryo-sac of 

 Angiosperms are gametes ; the megaspore has germinated directly into 

 a gametange ; the two median cells which have the polar nuclei for 

 their nuclear elements may be termed mesodes. He distinguishes be- 

 tween the uses of the terms albumen and endosperm ; — the former is 

 an abnormal sporophyte ; the latter a gametophyte. Supernumerary 



* Le Botanisto (Dangeard), vii. (1900) pp. 263-8. 



