April, 1920] PHYSIOLOGY 179 



basis of height at maturity, the constant K of the formula for autocatalysis is nearly the 

 same for all four groups; evidently, therefore, the differences in height between these quartile 

 groups were not due to differences in the growth constant. — 1 1 is concluded I bat the data indi- 

 cate that the course of the growth process is dominated by internal factors. — Howard B. 

 Frost. 



MOVEMENTS OF GROWTH AND TURGOR CHANGES 



1245. Smith, Erwin F. The cause of proliferation in Begonia phyllomaniaca. Proc. Na- 

 tional Acad. Sci. [U. S. A.] 5: 36-37. 1919.— A "synopsis" of a paper to be published in The 

 Journal of Agricultural Research. The leaves and stems of this begonia may proliferate as a 

 result of injury to the leaves, stems, or roots. The shoots produced may be very numerous, 

 though only a few establish permanent vascular connections and persist as true branches. 

 Either acicular or glandular hairs, as well as ordinary epidermal cells, may produce buds. 

 Only young cells are affected. The cause of proliferation is considered to be some cell change 

 due to a sudden checking of the water supply. — Howard B. Frost. 



1246. Van Ameijdex, U. P. Geotropisim and phototropism in the absence of free oxygen. 

 Recueil Trav. Bot. Neerland. 14: 150-216. 5 pi. 1 fig., 1917. [Received, 1919.]— Experiments 

 unlike those previously performed were done under normal atmospheric pressure and only 

 partial pressure of oxygen was reduced. A specially constructed thermostat was used in 

 which oxygen could be replaced by nitrogen by gradual diffusion. Avena saliva was taken 

 because it proved particularly suitable as used by other experimenters. Sinapis alba (p. 

 191), because of the absence of cavities under the cotyledon, was the other plant worked 

 with. A carbon filament lamp with photometric value 5 m.c. at one meter was the source 

 of light. Commercial nitrogen from cylinders had its small amount of oxygen (about 3.3 

 per cent, removed with alkaline pyrogallol. Owing to the fact that the gas so treated formed 

 a small quantity of carbon monoxide this had to be removed by passing the gas over heated 

 copper oxide in a combustion furnace until it had no longer a toxic effect on the plants. The 

 author found that it was necessary to deprive the seedlings of oxygen for a considerable time 

 to inhibit phototropic curvature. This is owing, first, to the fact that, due to intramolecular 

 respiration, the objects have sufficient energy at their disposal to enable them for a long 

 time to perceive stimulus and react, when after stimulation they have been supplied with 

 air; and, secondly, because it is possible that the intercellular cavities as well as the cavity 

 found between the coleoptile and the first leaf, may hold air a long time. The results of the 

 author agree with those of Correns in that oxygen is found necessary for the occurrence of 

 stimulus movements. There is disagreement with Correns, however, in that the author 

 finds the phenomena in geotropic and phototropic stimulation processes to be in all respects 

 much alike. The author claims to overcome the difficulties of other methods by eliminating 

 the variation due to partial vacuum while oxygen was removed from the plants, so that the 

 marked difference in results and conclusions reported are claimed as justification of this 

 criticism. When seedlings which had been long enough removed from the influence of oxygen 

 are stimulated geotropically or phototropically in the absence of oxygen and are then at once 

 placed in atmospheric air, they are unable to execute a reaction. If the seedlings are given 

 a similar fore-period in an oxygen-free atmosphere, and the stimulus is administered in air 

 in which the plants are left subsequently, a reaction does occur. In an oxygen-free environ- 

 ment the perception of a stimulus cannot therefore take place provided that the condition of a 

 sufficiently long fore-period has been satisfied. If after perception of a geotropic or photo- 

 tropic stimulus the seedlings are left in the oxygen-free-atmosphere, they do not react, so 

 that the presence of oxygen is also necessary for the occurrence of the reaction. In an atmos- 

 phere of low oxygen content the seedlings remain for a long time able to perceive normally, 

 but a prolonged stay in such an atmosphere weakens the power of perception. There are no 

 indications that on complete or partial withdrawal of oxygen the reaction of seedlings to a 

 geotropic stimulus differs from their reaction to a phototropic one. — J. A. Nieuwland. 



