6'JG summaby of current researches relating to 



klinostat ; and causing the water to rotate by the introduction of a 

 current while the object remains still. Of these methods he prefers the 

 third. With one exception (Soya hispida), Berg finds rheotropism to be 

 always exhibited by the roots of seedlings : normally the rheotropism 

 is positive ; but it readily passes into negative rheotropism at a low 

 temperature. 



Herr H. 0. Juel * has adopted a process resembling Berg's second 

 method. From experiments on decapitated roots he has determined that 

 the zone of growth is sensitive to rheotropism. He regards the phe- 

 nomenon as having nothing in common with hydrotropism. The upper 

 and lower limits of the rapidity of current which can give rise to 

 rheotropic curvatures vary greatly in different plants. The highest and 

 the lowest of all are given respectively as 20-30 cm. and 0*3 mm. per 

 second. 



Influence of the Curvature of the Root on the Production and 

 Arrangement of the Lateral Roots, j — Herr F. Noll maintains that the 

 unilateral arrangement of the rootlets on the convex side of curved roots 

 cannot be ascribed altogether to external forces, since the curvature 

 takes place whether the irritation be geotropic, heliotropic, or hydro- 

 tropic ; its explauation must be sought at least partially in internal 

 causes. Increase in thickness is not, under these conditions, the result 

 of an extra supply of nutriment ; the latter is rather the result of the 

 former, which is the product of specific irritation. 



Nutation of the Sunflower.} — Observations made by Prof. J. H. 

 Schaffner on Hclianthus annuus, both wild and cultivated, confirm the 

 popular idea of a gradual change in position of the flower-head according 

 to the time of day. The growing plants nutate from 60° to 90° W. in 

 the evening, and from 50° to 70° or more E. in the morning. At night 

 the leaves droop and the tips point downward. Similar results, though 

 less pronounced, were obtained with H. petiolaris. 



Peculiar Case of Contact-Irritability.§ — F. Grace Smith describes 

 a phenomenon connected with the growth of a number of " bush-beans" 

 from seed in the dark. When the seedlings, perfectly etiolated, were 

 about 20 in. high, and had developed their first leaves, the petioles had 

 all arranged themselves in parallel planes ; while no such adjustment 

 was displayed on seedlings grown in the light. Experiments were made 

 which seemed to determine that the phenomenon was not due to thermo- 

 tropism or hydrotropism ; it appeared to be entirely due to the near 

 contact of the petioles with one another. 



C4) Chemical Changes (including- Respiration 

 . and Fermentation). 



Nitrogen-Assimilation of Green Plants. || — Herr L. Jost reviews the 

 various theories which have been brought iorward on this subject, and 

 sums up in favour of Schulze's, which he summarises as follows: — The 



* Pringsheim's Jahrb. I wiss. Bot., xxxiv. (1900) pp. 507-38 (7 figs.), 

 t Landwirth. Jahrb., xxix. (1900) pp. 361-426 (S pis. and 14 figs.). Sec Bot. Ztg., 

 lviii. (1900) 2"> Abt, p. 281. 



X Bot. Gazette, xxix. (1900) pp. 197-200 (10 figs.). 



§ Bull. Torrey Bot. Club, xxvii. (1900) pp. 190-4 (17 figs.). 



\\ Biol. C'entralbl., xx. (1900) pp. 625-37. Cf. this Journal, ante, p. G08. 



