52 



XXXIV. W. B. Brierlev. " Orchid Spot Disease.'' Gar- 

 deners' Chronicle, 1919. Vol. LXV. No. 1676. 



A consideration of the several diseases of orchid leaves in- 

 cluded under the name " Orchid Spot " ; with notes on methods of 

 treatment. 



XXXV. j. Henderson- Smith. " The Killijig of Botrytis 

 Spores by Phenol.'* Annals of Applied Blolog-v, 

 1921. Vol. VIII. No. 1. 



It is shown that if Botrytis spores be exposed to the action of 

 0.4 per cent, phenol, the spores do not all die simultaneously, but 

 some die in a few minutes and some not till two or three hours have 

 elapsed. The curve showing- the numbers surviving- at different 

 times has a sigmoid shape. If the strength of phenol be progress- 

 ively raised, the curve becomes less and less sigmoid, approaching 

 the logarithmic type of curve. With the same suspension it is 

 possible to obtain either a logarithmic or a sigmoid curve accord- 

 ing to the strength of phenol used. Both types of curve are shown 

 to be explicable on the assumption that the individual spores differ 

 in resistance and that a frequency curve showing the distribution 

 in the resistance grades approaches the normal curve. The in- 

 fluence of the number of spores used is shown to be very consider- 

 able ; and the consecutive transition from the sigmoid to the loga- 

 rithmic type occurs, whether we raise the phenol strength, keeping 

 the spore number constant, or reduce the spore number keeping 

 the phenol constant, or use younger and younger spores. 



TECHNICAL PAPERS. 

 CROPS AND CROP PRODUCTION. 



XXXVI. Winifred E. Brenchley. "Useful Farm Weeds." 

 Journal of Board of Agriculture, 1918. Vol. XXV. 

 pp. 949-958. 



During the war the deficiency in supplies of every kind led to 

 a revival of interest in the uses to which many farm weeds can be 

 applied. If the need ever became sufficiently urgent, weeds might 

 serve many useful purposes, but with the restoration of more 

 normal conditions most of them have again fallen into disuse. 



Weeds have their uses in medicine, as dyes, manures, and 

 as fibre plants, but in times of stress they are most valuable as 

 fodder and human food. Couch grass, spurry, bent grass, nettles, 

 chicory, gorse and poppy cake can all serve as fodder, especially as 

 most of them, in addition to being nutritious, are obtainable in 

 large quantities. 



Chicory and *' salep " (Orchis inasciila) are the principal 

 weeds used as human food. Chicory has long been employed as a 

 substitute or adulterant for coffee, while salep enters largely into 

 the diet of people of Turkey, Persia and Syria. Many weeds pro- 

 vide leaves that have been used as substitutes for tea and coffee, 

 and the young tops of nettles, garlic and dandelion have been 

 frequently used as green vegetables by country folk. 



