156 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Burning is greater at the positive electrode than at the negative electrode. 



The high resistance of trees serves as a protection from lightning, and is greatly 

 influenced by temperature and moisture. Stahl states that the more thoroughly 

 wet a tree becomes the less susceptible it is to lightning stroke. Thus smooth- 

 barked trees — beech &c. — are considered to be more immune to lightning than 

 rough-barked trees — oak &c. — because they become thoroughly wet during 

 storms. Smooth-barked trees possess a better water-conducting surface, and 

 have a tendency to equalize the electrical tension between the atmosphere and 

 the ground, so that they are rendered less susceptible to kghtning. — A. B. 



Elm-Bark Beetle. By C. Hankins {Quart. Jour, of Forestry, vol. ix. No. 1, 

 p. 72 ; Jan. 1915). — In many of the elm-growing districts, as well as in parks 

 and amongst hedge and isolated timber, effects of these insects are all too apparent. 

 Trees are being attacked more or less, some showing the first effects, while others 

 are fast becoming stag-headed. The latter have a very unsightly appearance, 

 with their almost barkless branches and twigless boughs. There appears httle 

 doubt as to how the spread has become so general. In many cases fallen limbs 

 as well as felled or blown timber are allowed to he for long periods where they fall. 

 Sickly and dying stumps are frequently seen amongst healthy trees. In woods 

 and plantations large arms and blown trees are found rotting where they fell. 



Negligent treatment in keeping woods and plantations clear of fallen timber 

 materially assists the breeding of these insects. Wherever possible, windfalls and 

 dying trees should be removed early, otherwise the growing stock may be 

 endangered throughout a wide circuit. — A. D. W . 



Eremocitrus, A New Genus of Hardy, Drouth-resistant Citrous Fruits from 

 Australia. By W. T. Swingle (Jour. Agr. Research, ii. pp. 85-100, May 

 1914 ; plates). — The plant on which this new genus is based is Triphasia 

 glauca Lindl. (=Atalantia glauca Benth.). It is a gray-green shrub with hairy 

 leaves of the centric type, and slender spiny twigs, and otherwise profoundly 

 adapted to a desert climate. It is dormant during winter, and is apparently 

 adapted to resist considerable cold, for it appears to be exposed to a temperature 

 of 5 0 Fahr. at times in its native habitat. The author believes the plant may be 

 usefully employed in hybridizing with cultivated species of Citrus in order to 

 improve their drought- and cold-resisting powers. It has been grafted or budded 

 successfully on the orange, lemon, grape-fruit, Citrus australasica, tabog (Chaeto- 

 spermum glutinosa), and the Indian wood-apple (Feronia elephantum) . — F. J. C. 



Explosives in Agriculture. By H. C. Coggins {Agr. Gaz. N.S.W. vol. xxv. 

 pp. 857-860, 929-933 ; 11 figs.). — Gelignite is the most suitable explosive for 

 use in agriculture, e.g. subsoikng, making post-holes, clearing land from tree 

 stumps, and preparing the ground for tree-planting. The last two operations 

 are fully explained by means of diagrams. — S. E. W. 



Fumigation and Spraying. By H. Garman (U.S.A. Exp. Stn., Kentucky, 

 Bull. 172 ; 9 illus.). — A number of formulas are given of fumigating and spraying 

 mixtures to control insect and fungus pests. 



Many strengths of cyanide of potassium are given, but the author suggests 

 the following as being best for the purposes named : — 



To kill aphides or white fly on tender plants in greenhouses. 

 025 oz. cyanide of potassium \ 



0-30 oz. sulphuric acid ffor each 1,000 cubic feet. 



0-75 oz. water. J 

 For plants that are not tender, double the quantities as above can be safely 

 used.— C. P. C. 



Fumigation, The Influence of Temperature and Moisture on. By 



W. J. Schoen (U.S.A. Exp. Stn., New York, Tech. Bull. 30; June 1913). — 

 The results of experiments, in cyaniding, for the destruction of the brown-tail 

 moth (Euproctes chrysorrhoea Linn.) are set out. Contrary to accepted opinion, 

 high temperatures with a humid atmosphere proved far more destructive than 

 the opposite conditions. 



The dose used was 75 grains potassium cyanide to the cubic foot. Tem- 

 perature not less than 50 0 nor above 70° F. — C. P. C. 



Fruit Trees on Houses [Rev. Hort. Beige, Nos. 21, 22, 23, 24, Dec. 

 1913 ; figs.). — A series of articles on planting and growing fruit-trees against 

 houses. The writer gives information on choosing varieties, on training in all 

 sorts of ingenious ways in order to utilize every inch of available space, and on 

 the general care of the trees. — M. L. H. 



