FIELD CROPS. 829 



The physiology of the pollen of Trifolium pratense, J. N. Martin (Bot. Gaz., 

 56 (191.3), A'o. 2, pp. 112-126. fig. i).— The author states that " the investigation 

 of red clover pollen was begun with the hope that a thorough knowledge of its 

 physiology, in conjunction with the history of the embryo sac, might help to 

 overcome the uncertainty of clover seed production. . . The work has to do 

 with three questions : Conditions necessary for the germination of pollen ; the 

 stigma as a stimulative and directive factor in tube development ; and relative 

 potency of the pollen in self and cross-pollination." The following conclusions 

 are reached : 



"The ix)llen of T. pratense is physiologically different from that of T. hybri- 

 diim and T. repcns in respect to behavior toward sugar ;-(ilutions. The only 

 function of the sugar solution in the case of the pollen of T. Jii/hndnm is the 

 controlling of water supply. The germination of the pollen of T. pratense is 

 delicately adjusted to water absorption. The results of the investigation show 

 that the stigma produces no secretions which influence pollen tubes. The na- 

 ture of the pollen demands no other function of the stigma in its germination 

 than the control of the water supply. The pollen in self-pollination germinates 

 readily on the stigma, but the tubes traverse the style much more slowly than 

 in cross-pollination." 



A bibliography is given. 



On the relationship between the number of ovules formed and the capacity 

 of the ovary for maturing its ovules into seeds, J. A. Harris (Bui. Torrey 

 Bot. Club, 40 (1913), No. 8, pp. 447-455, figs. 2).— The author's investigations 

 have consiste<l chiefly in determining the correlations between the degree of 

 development of various somatic organs and the fertility of the fruit, the prob- 

 lem being to determine whether ovaries with a number of ovules above the 

 average are more (or less) capable of developing their ovules into seeds than 

 those below the average. 



From the tabulated and graphically represented results obtained from studies 

 carrieil out, he concludes that in dwarf varieties of garden beans there is but 

 a slight relationship between the number of ovules per ovary and its capacity 

 for maturing these ovules into seeds, although such a relationship Is said to 

 exist. So far as the materials available may be considered as representative of 

 the species it is generally negative, i. e., as the number of ovules formed In- 

 creases the capacity for maturing these ovules into seeds decreases. 



Bud variations in SoLiniim, E. Heckel and C. Verne (Compt. Rend. Acad. 

 Soi. [Paris], 151 (1913), No. 12, pp. 484-481). — In continuation of a previous 

 communication (E. S. R., 28, p. 530), the authors give an account of their 

 studies on the possibility of inducing mutation in a number of species of 

 Solanum. By means of the excessive use of fertilizers, particularly those hav- 

 ing a high nitrogen content, mutation has been observed in the tubers of 5 

 species, S. commersonii, S. maglia, S. tuberosum, 8. immite, and S. jamesn. 



FIELD CROPS. 



[Fertilizer experiments with field crops], A. W. K. De.Tong (Dept. Landb., 

 Nijv. en Handel [Dutch FAist Indies]. Mrded. Agr. Chcm. Lab., 1912, No. 1, pp. 

 40, pi. 1, figs. 2). — In fertilizer experiments with maize from 28 to 30 per cent 

 better results were obtained with superphosphate than with bone meal, guano, 

 and Thomas slag, bone meal ranking second. The results with sodium nitrate 

 were better than with calcium nitrate or sulphate of ammonia. In a fertilizer 

 experiment with cassava the largest increase in yield of roots was with calcium 

 nitrate, in comparison with sulphate of potash, Thomas slag, or combinations 

 of these. With cowpeas the largest yield of grain was with superphosphate, 



