480 



Lees (A. H.). " Reversion " and Resistance to " Big Bud " in Black 

 Currants. — Ann. App. Biol., London, v, no, 1, July 1918, 

 pp. 11-27, 6 plates. [Received 5th September 1918.] 



" Reversion " in black currants is caused by a check to the normal 

 terminal bud, resulting in its being replaced by a big bud, a killed bud, 

 a blind bud, or a flower bud, this being accompanied by an abnormal 

 amount of growth from lateral buds. 



" Big bud " is a disease of black currants due to the attack of mites, 

 which does not kill the growing-point, but stimulates it to make 

 irregular development. 



The symptoms characteristic of " reversion " are : — (1) " running oS " 

 of the fruit ; (2) an unusual amount of lateral wood growth ; (3) sharp 

 pointed leaves ; and (4) long thin mternodes. When caused by 

 the presence of mites, it can obviously be cured only by the elimination 

 of this pest, for which no satisfactory method has yet been devised. 

 Reversion due to Aphids should be curable by pruning away super- 

 abundant terminals, at the same time" taking care that the bush is 

 making strong growth ; while that due to terminal fruit-bud formation 

 is evidence either of faulty pruning, or of the poor condition of the 

 bush as a whole. 



The existence of an apparently mite-resistant strain of black currants 

 is explained by the fact that such plants are not really resistant, but 

 in fact so susceptible that the mite kills the growing-point in an 

 attacked bud, thereby cutting off its own supplies and perishing. 

 A few buds however become " big " and serve as a source of infection 

 the following year. 



A form of reversion occurring in young bushes before mites or 

 Aphids are present is as yet unexplained. 



Taylor (T. H.). Oviposition in the Celery Fly. — Ann. App. Biol, 

 Cambridge, v, no. 1, July 1918, pp. 60-61, 1 fig. [Received 

 5th September 1918.] 



The celery fly [Acidia heraclei] usually oviposits beneath the 

 epidermis of the under-surface of the leaf. A puncture is made by 

 the ovipositor, which then breaks down the adjacent cell walls, forming 

 a space in which the egg is laid, the process taking about 40 seconds 

 on the lower surface and 50 seconds when the egg is laid from above. 



Hatching takes place in about 6 days, the larva emerging through 

 the opposite end of the egg from the puncture. It then burrows 

 forwards, eating out a narrow gallery ; after a few da3's it mines in 

 all directions, producing a cavity that coalesces with other similar 

 ones, thus forming a compoimd blister containing several larvae. 

 This has given rise to the idea that A. heraclei oviposits on the surface, 

 like Pegotnyiu and other bhster-making flies, whereas it more closely 

 resembles the Phytomyzidae in its method of oviposition. 



Ball (E. D.). The Beet Leafhopper and the Curly-leaf Disease that 

 it transmits. — Utah Agric. Coll. Expt. Sta., Logan, Bull. no. 155, 

 June l9l7, 56 pp., 5 plates, 6 figs. [Received 2nd September 

 1918.] 



The various investigations that have been carried out with regard 

 to the curly-leaf disease of beets caused by Eutettix tenella, Bak. (beet 



