237 



healthy seedlings are described. True leaf-curl is transmitted by 

 Aphids, the extent of the infection depending on the development of 

 the Aphids as influenced by climatic conditions. Tomatos and other 

 Solanaceous plants can carry the disease without exhibiting the 

 symptoms as clearly as potatoes. In Holland during the summer 

 of 1921 Aphis rumicis (black aphis) was found to be abundant on 

 potato plants, whereas Myziis (Myzoides) pcrsicac is generally the 

 common potato Aphid. Mutual infection of the selected seedlings is 

 prevented by planting a row, about five ysLvds broad, of mangel, 

 beet or beans between the rows of potatoes, but in view of the 

 occurrence of A. rumicis on potatoes it may be necessary in future to 

 exclude beans and beet. 



Infection also apparently varies in different localities ; in heavy soils 

 near the sea the diseased plants infect only those nearest to them, 

 whereas on peat and sand the infection is carried over much greater 

 distances. The infection is also carried further in more sheltered 

 situations. Aphids are more abundant in the sheltered places and on 

 the sandy and peat soils than on the clay near the sea, where there is 

 practically a constant wind blowing. 



Cotton (A. D.). The Situation with regard to Leaf-curl and Mosaic 

 in Britain.— 7?t'/)/. Internal. Potato Conf., R. Hortic. Soc, London, 

 1921, pp. 153-166. [Received 8th March 1922.] 



The observations and experiments made in Britain tend to confirm 

 the discoveries of Dutch and American authors that leaf-curl and 

 mosaic diseases are highly infectious and that the virus is carried from 

 plant to plant by Aphids. The distribution of the two diseases in 

 England, Scotland and Wales is outlined ; although they may occur 

 in a severe form in all parts, they appear to be less prevalent in the 

 northern and upland areas. The relative importance of meteorological 

 and soil conditions and the presence of other food-plants in favouring 

 attack by Aphids is discussed, and the need for research is emphasised. 

 In Britain no special systematic work on the potato-infesting Aphids 

 has yet been carried out. In Holland, and apparently also in America, 

 the most usual species appears to be Myzus {Myzoides) persicae, 

 Sulz. {Rhopalosiphum dianthi, Schr.). 



It should be possible by persistent and ruthless roguing to eliminate 

 these diseases entirely. In certain districts early lifting may prevent 

 Aphid attack. The date of first migration depends greatly on tempera- 

 ture, and is an important point in determining whether the virus will 

 reach the tubers before the crop is lifted or cut off by the frost. 



Scott (H.) . Note on some Hymenopterous Parasites and other Enemies 

 of Tortrix viridana, Linn., with further Records of Chalcididae. 

 swarming in Buildings.— £/?/. Mthlv. Mag., London, h-iii, no. 694, 

 3rd Ser. viii, no 87, March 1922, pp. 56-61. 



It has now been proved that Pteromahis deplanatus, Nees, is a 

 parasite of Tortrix viridana, L., and further records are given of the 

 swarming of this Chalcid in houses [R.A.E., A, vii, 143]. Stenomalus 

 muscarum is also recorded as swarming in houses, but very little is 

 known about its hosts, though it is said to have been bred from puparia 

 of Muscid flies. 



Other enemies of T. viridana are the Ichneumonids, Phaeogenes stimu- 

 lator, Grav., widely distributed on the Continent, Pimpla brassicariae, 

 Poda, and Labrorhychus nigricornis, Wesm., and also, according 



