826 EXPERIMENT STATION EECOED. 



and their cleavage products. The percentage germinating after treatment 

 and the rate of growth of roots and stems were investigated in each case as 

 affected by the different substances and the results given in connection svith 

 each. 



Light intensity and substratum as related to germination, A. Ottenwaldee 

 (Ztschr. Bot., 6 (1914), No. 10, pp. 785-848, figs. 8). — Experimentation similar 

 to that of Lehmann (E. S. R., 2S, p. 327) is said to have shown that germina- 

 tion of seeds depends largely upon temperature, but both this requirement and 

 that of light are found to differ, not only in general with species, but individu- 

 ally with age and parentage. The light requirement as regards intensity is 

 closely related to temperature, the former increasing as the latter is lowered. 

 The illumination period is related also to temperature, but more closely to light 

 intensity. Seeds which are sensitive to light are also strongly influenced by 

 weak acids. 



The hypothesis of a catalytic influence of light is said to have received 

 support from these observations. 



A bibliography is appended. 



The influence of light from the mercuiy vapor lamp on the germination 

 and early growth of plants, W. Carl (Beltr. Biol. Pflanz., 12 (1914), No. 3, 

 pp. 435-437, pi. 1). — The author states that ultraviolet rays were found to 

 exercise an injurious influence on sprouting plants as regai-ds both germination 

 and subsequent development in the early stages. This is claimed not to be due 

 to warmth or to ozone but to the chemical influence of the ultraviolet rays. 



The influence of light on etiolated leaves, E, Schonfeld (Beitr. Biol. 

 Pflanz., 12 (1914), No. 3, pp. 351-412, figs. 55). — Reporting experiments with 

 light influence on numerous plants, mostly of familiar species, the author 

 states that individuals whose leaves had remained small in darkness usually 

 renewed growth measurably with access of light, this response, however, being 

 weaker in older leaves and in general stronger in the younger parts. Beyond 

 a certain point no response was obtainable. 



On account of the fact that recovery may be limited to certain portions, 

 abnormal leaf forms may result, some of which are described. Recovery of 

 color and renewal of growth are held to be separate phenomena, the former 

 always preceding. The longitudinal growth of parallel veined etiolated 

 leaves when brought into the light is checked, but these show a tendency to- 

 ward attainment of normal breadth. 



A bibliography is appended. 



The influence of humidity and illumination on growth in length of seed- 

 lings, Helene Jacobi (Osterr. Bot. Ztschr., 64 (1914), No. 3-4, PP- 94-101; ahs. 

 in Bot. C'entbl., 126 (1914), No. 9, p. 212). — Continuing previous work (E. S. R., 

 28, p. 227), the author has investigated the joint effects of moisture and light 

 on plants. 



It was found that in experiments carried out with bean seedlings in moist 

 air where the product of light intensity by exposure period was a constant a 

 larger value of the time factor was needed than heretofore to produce retarda- 

 tion of growth ; that is, the presence of moisture decreased the effect of the in- 

 tensity factor on the growth of the plant. 



The influence of air movements on illumination of foliage, J. von Wiesnee 

 (Ber. Dent. Bot. Gesell., 32 (1914), No. 8, pp. 555-565).— This is a discussion of 

 the tendencies noted of leaves on certain plants to assume positions habitual 

 or advantageous in direct or in diffused light or to return to such positions 

 after being disturbed by wind of longer or shorter duration and of the loss of 

 this tendency in aging leaves. 



