AGEICULTURAL BOTANY. 129 



minimum before 3 o'clock. The growth of the opuutias takes place during 

 a period of decreasing acidity, resulting from the disintegrating action of light 

 and rising temperatures. This statement, it is believed, applies not only to 

 the diurnal behavior of the plants during the grow^ing season, but to the grovr- 

 ing season as a whole. 



In conclusion the author states that light and temperature in lesser degree 

 are seen to exercise a totalized releasing effect on gi'owth coincident with 

 reduced acidity and increased hydratation to a certain limit. Beyond this 

 growth is checlced. 



The time and distance relation between brief illumination and reaction in 

 sprouting vetches, G. Campanile (Atti R. Accad. Lincei, Rend. CI. Sci. Fis., 

 Mat. 6 Nat., 5. so:, 23 (lOU), I, No. 12, pp. 966-969).— This gives in tabular 

 form the responses by sprouting vetches after an exposure of one second to a 

 light of 50 candlepower at distances of 1 to 4 meters. Distance does not ap- 

 pear to affect the degree of curvature, but the percentage of preceptible re- 

 sponses increases with the time from zero at all distances employed for half 

 an hour to 58, 25, 22, and 14 per cent at 1, 2, 3, and 4 meters, respectively, 

 for 2i hours, and 100, 98, 82, and 70 at these distances for 10 hours. 



On the identity of heliotropism. in animals and plants, J. Loeb and H. 

 Wasteneys (Proc. Nat. Acad.. Sci., 1 {1915), No. 1, pp. H-Ifl). — ^Attention is 

 called to the fact that the investigations of Blaauw (E. S. R., 22, p. 329) 

 showed that the time required to bring about the hellotropic curvature of plant 

 changes inversely with the intensity of illumination, and that the same law 

 holds for the lieiiotropic curvature of the polyps of Eudendrium. 



Some further investigations have been conducted to compare the relative 

 eflBciency of the various parts of the spectrum upon the production of hello- 

 tropic curvatures in Eudendrium with that found for the hellotropic curva- 

 tures in plants. These showed that the relative efficiency of the different parts 

 of the si>ectrum of a carbon arc light for the production of hellotropic curva- 

 tures in Eudendrium and in seedlings of Avena is practically identical. 



The coefficient of mutation in CEnothera biennis, H. DeVries {Bat. Gaz., 

 59 {1915), No. 3, pp. 169-196).— The author gives the results of a study of 

 about 8,500 individuals grown from seeds taken from pure line pedigreed 

 plants of CE. hiennis. 



There were found among these specimens 8 nanella, 4 semigigas, and 27 

 sulfurea mutants, giving percentages of about 0.1, 0.05. and 0.3 per cent. The 

 origin of mutants from other species, the question of partial sterility, and 

 other mutation factors are discussed at some length. The author considers the 

 phenomenon of mutability observed in CE. lamarckiana, CE. hiennis, and allied 

 forms, as a simple continuance of the supposed mutability which presided at 

 the origin of the wild species of the evening primroses. 



In connection with his investigations, it was found that the seeds of evening 

 primroses were often very slow in germinating. This difficulty, it is said, can 

 be overcome by pressing water into them, a pressure of 6 to 8 atmospheres for 

 from 1 to 3 days being sufficient to stimulate all to a rapid germination. 



An interpretation of self-sterility, E. M. East {Proc. Nat. Acad. Set., 1 

 {1915), No. 2, pp. 95-100). — The author offers a suggestion as to the cause of 

 sterility based upon a study of descendants of a cross between Nicotiana for- 

 getiana and the large white-flowered variety commonly known as 2V. affinis. 

 A large number of experiments in which plants were self-crossed and back- 

 crossed through several generations were made and studies were conducted 

 with pairs of plants which furnished series of selfed and crossed flowers. In 

 these the pistils were examined at regular periods and the difference between 

 the development of the pollen tubes in the selfed and crossed styles was found 



