044 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



lelts of mycelium develop, followed by sclerotia. The leaves are par- 

 ticularly liable to attack; the buds, stems, and roots less so. The 

 mycelium persists in the soil, and infection comes from the sub- 

 terranean to the aerial portions of the plant. The mycelium appears 

 to be sterile, nor has spore formation from the sclerotia been observed. 

 The fungus is European in distribution as well as American, and is 

 Sclerotiuin rhizodes, Auersw. — F. J. C. 



Growth of Wheat Seedling's. By J. F. Breazeale and J. A. 

 Le Clerc {U.S. A, Dep. Agr., Bur. Chem., Bull. 149; March 1912; 

 8 plates). — This is a physiological study on the effect of the reaction 

 of the culture medium on the growth of wheat seedlings undertaken 

 primarily to determine whether or not the results obtained in practical 

 agriculture can be explained in the laboratory 'from a purely scientific 

 standpoint. The experiments were carried on in nutrient solutions 

 and in distilled-water cultures, thus eliminating the disturbing factors 

 due to the presence of soil grains. There were solutions of sodium 

 nitrate, potassium chloride, potassium sulphate, hydrochloric acid, 

 and sulphuric acid, and also of each of these with calcium carbonate 

 added (p. 6). The dry weight of the roots was increased in every case 

 by the addition of calcium carbonate (p. 11), but the dry weight of the 

 tops was not necessarily greater, though they were larger and pre- 

 sented a much better appearance, thus indicating that the appearance 

 of the stems of young wheat seedlings is not always a criterion of the 

 vigour of the plants and, therefore, of the probable yield of the mature 

 crop (p. 9). The experiments are considered to have shown very 

 clearly the extent to which selective action is practised by the roots. 

 Solutions which at the beginning of the experiment contained 150 parts 

 per million of potassium sulphate (87 parts of SO^ and 63 parts of 

 potash per milhon) were found at the end to have lost all their potash, 

 while only 30 parts per million of SO^ had been absorbed (p. 11). 

 Thus the solution becomes acid, and root development is injuriously 

 affected. 



It has been found that the enzymic activity of a wheat seedHng is 

 greatest during the first few days of its growth, this being especially 

 true of the oxydases and peroxydases of the root tip, and the effect of 

 toxic bodies upon this is an important factor both in agricultural prac- 

 tice and in scientific research. This was shown when growing a second 

 crop of seedlings in the same solutions after the first crop had been 

 removed, the acidity of the solutions to which the calcium carbonate 

 had not been added having developed to such an extent that in the 

 second crop the action of the enzymes was practically inhibited by 

 it, and the plants were unable to tide over this critical period (p. 14). 

 In the second crop the alkalinity of the solution (the addition of calcium 

 carbonate) increased both the green and the dry weight of the tops, 

 while the weight of the residual seeds was diminished, the acidity of 

 the solution preventing the food material that was stored up in the 

 seed from being transported into the plant. — A. P. 



