6l8 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



acid (i oz. to i gallon), or a dilute solution of ammoniacal coppei 

 carbonate applied some little time before the sowing of the seed, was 

 found in many cases an effective preventive of damping-off. 



The use of poor seed, giving rise to weak seedlings, leads to much 

 trouble. — F. J. C. 



Crop, The Effect of one Growing, on Another. By the Duke 

 of Bedford, K.G., F.R.S., and Spencer U. Pickering, M.A., F.R.S. 

 (Wohurn, 14th Rep., 1914, pp. 46-50). — The authors' investigations 

 into the effect of grass on trees are now widely known (see 3rd Rep., 

 1903, and 13th Rep., 1911), and an appendix to this Report (pp. 136-151) 

 gives a brief summary of their work in this direction during a period 

 of nearly twenty years. Recent experiments are considered to throw 

 light upon the subject and to explain many phenomena which have 

 hitherto been perplexing. The conclusions arrived at are that a toxic 

 substance is formed in the soil by the growth of any plant in it, 

 originating probably in the decomposition of the debris of roots during 

 growth, this substance being toxic, not only to other plants of a 

 different nature, but to the plants themselves which form it ; but that, 

 by the action of air and moisture, probably with the assistance of 

 bacteria, this toxin becomes oxidized and converted into plant food, 

 thus eventually rendering the soil more fertile than it would be in 

 the absence of vegetation. This beneficial action takes due effect on 

 any plants growing in the soil, unless these have been so injured by the 

 previous toxic action as to be beyond recovery, as in the case of trees. 



This Report also contains a communication on the subject by Dr. 

 E. J. Russell, the Director of the Rothamsted Station (pp. 51-68). 

 A seven years' series of pot experiments have been conducted there in 

 v/hich rye, buckwheat, and spinach have been grown during the 

 whole period in the same soil, and these show that no lasting toxic 

 effect is produced on the soil by any of the crops grown. The toxic 

 substance produced is very unstable and soon loses its poisonous 

 properties. The phenomenon seems to be general, being caused by all 

 roots and affecting all plant life so far as investigation goes. Efforts 

 to discover if the toxin is produced by some action of the roots on the 

 soil have so far given negative results. Certain experiments at Rotham- 

 sted indicate the possibility that bacterial action may play a part 

 in determining the injurious effects of the grass roots, for, apparently, 

 when the experiment was carried out under rigidly aseptic conditions 

 no harmful effects were obtained. — A. P. 



Currants and Gooseberries, Two new Insect Pests of. By R. A. 



Cooley {Jour. Econ. Entom. vii, pp. 193-195 ; April 1914). — The 

 laxva of small weevil {Pscudanthonomus valid'us Dietz) was found 

 feeding in the seeds of the currant and the tender younger parts of stems 

 of gooseberries, and red and black currants were found to be distorted, 

 undersized, and showing markings due to the attacks of a thrips {Lio- 

 ihrips montanus). Notes are given on the life-histories of the pests, 

 and " Black Leaf 40 " (nicotine solution) was found to be an effective 

 spray for the latter. — F. J. C. 



