AGRICULTURAL BOTANY. 627 



The relation of cultivated plants to certain soil salts, III, B. IIansteen 

 Crannee {Jahrb. Wiss. Bot. [Pring>ihcim], 5S {1914), ^'o. .}, pp. 536-602, pis. 3, 

 figs. 5). — This report gives a fuller and more detailed account of studies by 

 the author, previously uoted from another souiTe (E. S. R., 2S, p. 426), and 

 following up earlier communications on the same subject (E. S. R., 2r5. pp. 

 28, 328). 



Effect of strongly calcareous soils on the growth and composition of 

 certain plants, P. L. Gile and C. N. Ageton {Porto Rico Sta. Rpt. 1913, pp. 

 l-'f, 1.5). — A study has been made of pineapples, beans, radishes, sugar cane, 

 sweet cassava, and rice to determine the effect of varying the quantity of car- 

 bonate of lime upon their growth and composition. 



Some plants showed a variation in their ash composition, but in general 

 the results indicate that if a soil is not absolutely deficient in calcium it is 

 useless to attempt to increase the lime content of forage plants by liming the 

 soil. 



Quantitative criteria of antagonism, W. J. V. Osteehout {Bot. Oaz., 58 

 {1914), No. 2, pp. 178-186, figs. 4)- — In order to bring about more uniform 

 methods of determining antagonism, the author presents data which indicate 

 that the method of mixing equally toxic solutions furnishes the best criterion 

 of antagonism, since it is known at the outset just what effect each mixture 

 must have, provided there is no antagonism. Mixtures of two equally toxic 

 solutions must have precisely the same effect on growth as the pure solutions 

 themselves, provided the effects of the salts are additive. If antagonism exists, 

 there is an increased growth in the mixtures, and the amount of this increase, 

 expressed as percentage of the growth obtained in the pure solutions, is the 

 most satisfactory measure of antagonism. It is said that the most reliable 

 results may be obtained by the use of uniform material and by taking for 

 measurement only such parts as come into immediate contact with the solution. 



The effect of one crop upon another, Duke of Bedford and S. U. Pickebing 

 {Jour. Agr. ,Sci. [Englatid], 6 {1914), No. 2, pp. 136-151, pi. 1).—In continuation 

 of their investigations (E. S. R., 26, p. 639), in which the authors claim that 

 grass roots interfere with the growth of orchard trees, experiments were car- 

 ried on in earthenware pots in which tobacco, tomatoes, barley, and mustard 

 each were grown in one pot, surrounded by a second containing the same kind 

 of soil, but in which was grown not only various grasses, clovers, etc., but the 

 same plants as in the first pot. 



The I'esults of this investigation are given in some detail, and it is claimed 

 that every growing crop results in the formation of a substance which is toxic 

 to the growth of other plants and still more so to itself. By oxidation this 

 toxin loses its toxic properties and enhances the fertility of the soil. The toxic 

 effects is found to vary with the nature of the soil, the kind of plant, and the 

 vigor of growth. There is not believed to be any reason for assuming the 

 exci'etion of any toxic matter fi'om a plant, as the debris fi-om the growing roots 

 is believed sufficient to account for the formation of toxin. Heating of soil 

 produces toxic matter from organic substances present in it and in much greater 

 quantities than that produced by the growth of a crop. In both cases the 

 toxin, after oxidation, increases the fertility of the soil. 



The spread of morbid changes through plants from, branches killed by 

 heat, H. H. Dixon {Set. Proc. Roy. Dublin Soc., n. ser., 14 {1914), No. 12, pp. 

 207-210, figs. 2). — In a previous publication (E. S. R., 17, p. 452) the author has 

 shown that if a branch of a plant Is killed by heat and the rest of the plant 

 supplied with water through this branch, some of the leaves on the uninjured 

 branches may become injuriously affected. Further studies have shown that 

 branches killed by heating tbem with steam and afterwards supplying them 



