Vol. XII. No. 280. 



TUH AOItlCLLTUllAL NKVVS. 



til 



trees which are dead or dying as a result of attacks of 

 these beetles. 



lor.x. The com ear worm (Lap/ti/f/ma Jrufjiperda) 

 occurred in unusual numbers in llie Southern United .States 

 ■tluring 1912, and in Tiinidad also it was more than ordin- 

 arily abundant. An acccunt of ihise occurrences was given 

 on p. 346. 



MANGOES. Sevtral species of fruit Hies attacking mangoes 

 were mentioned in an article entitled Mangi I'ests in the 

 3'hilippines (.see p. 106); other in.sects capable of cau.sing 

 .serious injury to mangoes mentioned in the same article are 

 the so-called mango flies — two species of the genus Idiocerus. 

 These are Hemipterous insects wliich with their sucking 

 uioutli parts damage the buds and tender twigs. 



O.*c.\o. The method of trapping the cacao beetle (Sh ii-n- 

 stoma dtpre'Hii III) which had been found successful in Trinidad 

 was described on p. 31 -i. 



This account will be continued 



CHANGES IN CALCIUM CYANAMIDE. 



A paper dealing with thi- changes in caiciuni 

 cyanamide in a temperate climate is thus abstracted 

 in the Bulletin nfthe Bureau of Agricultural Intelli- 

 gence and of Plant Diseases for October 1912: — 



Calcium cyanamide, esjjeci illy if it is in a more or less 

 moist medium, ab.soibs a certain amount of water and 

 carbonic acid which go to increa.se the weight, and result 

 con.sequently in a reduction of standard; it is doubtful, 

 however, whether in correspondence herewith a real and 

 .genuine loss of nitrogen must be assumed to take place. 



Taking up this question, the writer has carried out 

 a series of researches on three specimens of calcium cj'ana- 

 inide kept for periods of twenty-five and fifty days, both 

 jn a dry and a moist medium. The losses of nitrogen were 

 eslimated directly, by collecting and ascertaining the quantity 

 of ammonia given c.ti' during the experiment; indirectly, by 

 making a determination of the nitrogen before and after the 

 •experiment, with an innovation in the method inasmuch as 

 the determinations made after the experiment were carried 

 out on quantities of material weighed before the experi- 

 ment, and afterwards submitted in their entirety to analysis, 

 so as thus to obtain the real and actual loss of nitrogen, 

 independently of any variation of weight undergone by the 

 fertilizer. In both cases the specimens were kept in bell jars 

 through which a slow current of air driven by a fan passed. 

 The results obtained show that calcium cyanamide df^es 

 etiectively undergo a loss of nitrogen, which, however, even 

 in a moist medium is very small. In this experiment the 

 material was spread out and broken up, so that it had a large 

 surface expo.sed to the action of the moisture which causes 

 the loss of nitrogen, while under real practical conditions this 

 does not take place, nor is the material kept in media 

 saturated with moisture; for this rea.son, the writer is of 

 opinion that in practice the losses to be apprehended will 

 be almost ml or very small, especially if the medium is not 

 •very moist. 



In a second series of enquiries carried out on the same 

 materials and under the same conditions, the writer concerned 

 him.self with the variations undergone by nitrogen in the 

 cyanamide form. From the results he notes that nitrogen in 

 this form undergoes constant diminution in the course of 

 time; this diminution, though small is a dry medium, 

 increases considerably in the open air, and may result in the 

 almost entire disappearance of the cyanamide form in a moist 

 snedium. He therefore thinks that in calcium cyanamide the 

 progressive conversion of the nitrogen in the cyanamide form 



into other forms, which remain in the manure, is produced by 

 the action of moisture. 



Finally, in a third series of investigations, the writer 

 studies the course of this transformation in the aqueou.s 

 solution of calcium cyanamide, likewise extending his atten- 

 tion to the dicyaniliarnide form. He works with concentra- 

 tions of 1 per cent, and •'> per cent, at a constant temperature 

 of 27° C. The percentage of cyanamide and dicyandiamidu 

 nitrogen, determined at variou.n intervals of time, are summeil 

 up in a table and re['resented graphically in two diagrams: 

 which show: — 



(1) That the cyanamide form diminishes continuously 

 until com[ilete disappearance, with greater speed in the more 

 concentrated solution. 



(2) That the dicyandiamide, which is nil or almost nil 

 at the start grows rapidly to a maximum, after which it 

 diminishes continuously, and the phenomenon is more pro- 

 nounced in the more concentrated solution, in which thfe 

 formation of dicyandiamide is greater. 



A notable fact in these solutions is the formation of crys- 

 tals of calcium hj-drate, while the formation of ammoniacal 

 compounds does not take pi ice; a mixture of two or three 

 different crystalline forms of deliquescent nitrogenous 

 compounds, melting below 100° C, which was isolated from 

 the solution, appears to contain the final forms into which 

 the nitrogen of the calcium cyanamide passes. It must 

 be held, therefore, that the conversion of the cyana- 

 mide in the soil must not be attributed exclusively to physico- 

 chemical causes determined by the presence of zeolites* and 

 colloids! in general, but must in great part be due to the 

 action of the calcium present in the substance. 



A Work on Tropical Products.— There has 



been [jublished lately, in (lernian, an aid in botany for 

 planters, colonial oflicers, business men in the tropics and 

 travelling investigators {Jiolaiiiarhes llilfsliuvh fiir Plian\vt\ 

 KiiloniaVmniUi', TropinknutJi uti and Forschunijsri'isende), by 

 Dr. Hubert Winkler. This is reviewed in Dn- Tropetipdan.'-r 

 for December 1912, which commences by emphasizing that 

 the want has long been felt for a book in which the unpro- 

 fessional man may find, in a closely abbreviated form and 

 alphabetical order, the most important facts concerning usefuV 

 tropical plants. The book is stated to be to a certain extent 

 a counterpart of Ferdinand von Midler's .'^ilert Extra fropicil 

 Plants, which is no longer published in English, but has been 

 translated nevertheless into ( lerman; it is now so out of dat»? 

 that it requires to be rewritten. The work mentioned actually 

 dealt only with extra-tropical plants. Winkler's book is really 

 concerned with tropical crops which possess importance from 

 the standpoint both of Germany and her colonies. 

 The greater part of the book contains descriptious of the 

 crops and information concerning their culture, uses, and so 

 on; and there is given a detailed table, in the order of the 

 botanical names of the plants, carefully arranged, together with 

 the common names; another table classifies the matter under 

 the names of the products. The book is stated to be 

 cheap, and it is expected that it will have a wide sale, par- 

 ticularly as a supplement to the statistics concerning raw 

 materials that are found in the libraries of large com- 

 mercial firms— those engaged in trade as well as those 

 concerned with planting. The work is published by the 

 Hinstorttsche \'erlagsbuchhandlung, W'ismar. 



♦Minerals soluble in acids, in which most of them deposit 



silicii. 



tSuhstJvncos which pass .inly exceedini-dy .slowly throu-^l* 

 a piirous mcnibrane. 



