366 SUMMARY OF CURRENT RESEARCHES RELATING TO 



results, which confirm those obtained by De Saussure, are as follows : — 

 The respiratory quotient of the reproductive organs is much greater 

 than that of the leaves. The respiratory quotient of the pistil is 

 usually greater than that of the stamens ; in the plants examined 

 ( 'anna indica was the only exception. The respiratory intensity of the 

 anther is greater than that of the filament. The intramolecular respira- 

 tory intensity is usually greater in the reproductive organs than in the 

 leaves ; Lavatera Olbia forms an exception, and in Cheiranthus Gheiri 

 and Tropseolum majus there is very little difference between the respira- 

 tion of the stamens and pistil and that of the leaves. The intramole- 

 cular respiratory intensity of the pistil is again greater than that of the 

 stamens, with the exception of Acanthus ; in Ornithogalum arabicum the 

 two intensities are about equal. 



Irritability. 



Chemotaxis of Spermatozoids of Lycopodium.* — H. Bruchmann 

 has made experiments upon the spermatozoids of Lycopodium, and 

 concludes that they are attracted to the archegonia by the chemotactic 

 action of free citric acid or of solutions of several of its salts. Although 

 it is impossible to detect the acid in the contents of the archegonium or 

 the neighbouring cells, the sap of the prothallium is weakly acid. The 

 presence of the acid is probably due to the saprophytic mode of life of 

 the prothallus, and perhaps to the presence of an endophytic fungus ; it 

 appears to form a protection against the attacks of insects, but to be the 

 means of bringing about fertilisation. Spectrum-analysis confirms the 

 presence of the acid. 



Hygroscopic Movements of Leaves, j — W. Lorch replies to a remark 

 made by Steinbrinck in his paper on the mechanism of cohesion in the 

 rolling and folding leaves of Polytrichum commune and of certain dune- 

 grasses. % Lorch maintains, in opposition to Steinbrinck, that there is in 

 the leaves of Polytrichum commune a mechanically weaker part which 

 acts as a sort of joint, and that it is situated in the median line of the 

 dorsal sclerenchyma plate. And he disagrees with Steinbrinck in 

 several other points. 



£ General. 



Castration in Zea Mays produced by Ustilago.§ — M. Chifflot pub- 

 lishes a note describing observations made upon " parasitic traumatism " 

 in connection with Zea Mays. The female and hermaphrodite flowers 

 of inflorescences attacked by the fungus have much modified stamens. 

 Even when the latter appear to be normal externally, it is found that 

 the pollen is often not shed, and the grains themselves are greatly 

 modified in structure. In the hermaphrodite flowers the ovary never 

 attains maturity. The purely female flowers undergo no reduction and 

 yield perfect seeds. In conclusion, the author states his belief that 

 traumatism, however caused, produces thelygenous castration, and that 

 Laurent's theory respecting these anomalies is perfectly admissible. 



* Flora, xcix. (1909) pp. 193-202 (1 fig.). 



t Ber. Deutsch. Bot. Gesell., xxvii. (1909) pp. 51-6. 



X Op. cit., xxvi. (1908) pp. 399-412. 



§ Comptes Kendus, cxlviii. (1909) pp. 426-9. 



