No. 1, July, 1920] FORESTRY 69 



455. Pack, C. L. Central Park trees starving to death. Amer. Forestry 25: 1391-1400. 

 SO fig. 1919.— Of some 60,000 trees in Central Park, New York City, WOO or more have died 

 since 1917, chiefly during the severe inter of 1917-1918. The trees which died would, in the 

 large majority, have withstood the inter had they no1 been weakened by long years of 

 malnutrition. Of the 3000 dead trees removed in the last 2 years, the greater number wore 

 Oriental plane trees; next in number of dead were the elms; third came the oaks and Lom- 

 bardy poplars; fourth, the lindens; and last, the maples and several other species. The con- 

 ditions which have led to the death of these trees and the poor condition of o<hers are (1) 

 shallow soil, heavy impermeable clay and hard packing of soil around trees and (2) unfavor- 

 able meteorological conditions (there has been a decided decrease in rainfall in the last 20 

 years, and much of this decrease has been in the summer months when needed most; there has 

 been a decided decrease in relative humidity in the past 5 years, coupled with an increase in 

 the wind movement during the same period; and the trees were subjected to a very severe 

 frost in the winter of 1917-1918).— Chas. II. Otis. 



456. Pattox, R. T. Timber production and growth curves in the mountain ash [Euca- 

 lyptus regnans.] Proc. Roy. Soc. Victoria. 30 1 : 1-3. Pl.I-II,fig. 1-4. 1917. [Received 1919.] 

 — Studies of the annual rings of logs were maae at Powelltown. The timber was considered 

 to be over ripe and many trees showed incipient decay in the heart. It was generally possible 

 to distinguish clearly 80 annual rings. The outer rings beyond these were narrow and less 

 clear, although in one case 125 rings were counted. It was concluded that the tree reached 

 its prime well under 100 years. A remarkable trunk expansion occurred during the first 10 

 years. The ring width from decade averages for the whole period was shown to decline stead- 

 ily, probably partly due to overcrowding. Less variation in ring width occurred after the 

 30th year. The increase in diameter of trees, indicated by decade averages, was so regular 

 (curve) that age could be closely estimated from it. If x represented the age of the tree and 

 y represented the diamater in inches, then Syjx = y approximately. The amount of wood 

 produced during the second decade of growth was twice that for the first. The maximum 

 growth occurred in the 5th decade, after the 40th and before the 50th year. The minimum was 

 not fully established. Although the tree reaches maturity (maximum growth) at about 50 

 years it is not then fit for milling. The growth for the next 10 to 20 years would be, under 

 the local conditions, profitable financially if the crowns remained vigorous because the wood 

 would mature and improve by ripening. In a tree still healthy at 80 years, heart rot was not 

 to be feared. It was found that young trees were not attacked by mistletoe. The decrease 

 in vigor, indicated by the rings and the paucity of foliage, which generally occurred after 70 

 years, marked a loss of vitality which was thought to make the tree subject to attacks of all 

 kinds. — Eloise Gerry. 



Si 



457. Petraschek, Karl. Einiges iiber die angewandte Entomologie in Amerika and ihren 

 Einfluss auf die entomologischen Reformbestrebungen in Deutschland und Deutsch-Oster- 

 reich. [Notes on applied entomology in America and its influence on the movement for ento- 

 mological reform in Germany and German Austria.] Forstwiss. Centralbl. 41 : 161-173. 1919. 

 — The biological method of combating insect pests (by favoring the development of their nat- 

 ural enemies) was first suggested to the author in connection with ravages of the gypsy (Ly- 

 mantria diipar L.) and brown-tail moths (Euproctis chrysorrhoeah.) and the oak caterpillar 

 (Cnethocampa processiona L.) on the south slopes of the Transylvanian Alps in Roumania 

 in 1S87, and in Croato-Slavonia and Bosnia in 1889. This method has been developed on an 

 extensive scale in the United States, under the leadership of the Bureau of Entomology (a 

 number of instances are given) and other methods have also been widely studied, especially 

 the use of chemicals. The success of American entomologists in this work, which requires a 

 very thorough detailed knowledge of the insects, their life habits, and their enemies, is attrib- 

 uted to their capacity for going deeply and thoroughly into a study and to their adaptation 

 to observational investigation of practical value, but primarily to the organization of ento- 

 mological research activity, with its division of work among specialists, and its centralization 

 or correlation by a central agency at Washington. — Prof. Escherich has been striving for de- 



