March 6, 1902 J 



NA rURE 



413 



LETTERS TO THE EDITOR. 



[ The Editor does iiot hold hiiiiscif responsible for opinions ex- 

 pressed by his eorrespondents. Neither ean he undertake 

 ip return, or to cot respond with Ike writers of, rejeclei 

 manuscripts intended for this or any other part of Nature. 

 N^o notice is taken of anonvinous communications,'^ 



Botany by Indian Foresters. 



A GLANCE at the Indian Forester for February affords 

 a complete refutation of recent charges brought against the 

 Indian Forest Department for neglect of botany. 



This number commences with a most able and interesting 

 account of the forests of the Sudan, written by Mr. Muriel, of 

 the Indian Forest Department, who was sent last year to 

 examine the forests along the Blue and White Niles and the 

 Bahr-el-Ghazel. After travelling for 4600 miles, Mr. Muriel 

 wrote a description of the chief components of the Sudanese 

 woodlands and savannahs, and especially of the cultivation of 

 Acacia verek, the Sudanese gum tree, from which last year 

 So,cxx> cwt. of gum, valued at 8o,ocx3/. , was delivered at 

 Khartum. 



Ordinary timber is valued at 2.S. a cubic foot at Khartum, 

 while large quantities of wood fuel are required for steamers on 

 the Nile and for locomotives, as well as for culinary purposes, 

 so that the importance of the protection of the forests against 

 incendiary fires and unrestricted grazing and felling is evident. 

 Mr. Muriel has given a very interesting account of the fauna 

 of these regions as well as of their flora, and it is satisfactory 

 to learn that the very able forester and botanist, Mr. A. F. 

 Broun, who has recently assisted Sir D. Brandis at Kew in his 

 new book on the Indian forest flora, has been appointed Con- 

 servator of Forests in the Sudan. 



In the same number of the Indian Forester is a paper by 

 Mr. A. W. Lushington, of the Indian Forest Service, on the 

 identification of seventy-four Indian species of Loranthacece by 

 means of their ramification and leaves. He states that it is not 

 uncommon in southern India to find forests completely ruined by 

 these parasites. "The vegetation, weakened by forest fires, 

 is incapable of battling with these pests, and as the better 

 species of timber trees are less well supplied with sap than the 

 inferior species, the former are the first to be killed." As the 

 LoranthacecE are classified by their flowers and the latter exist 

 only for a short period, while the forest officer has a very large 

 district to supervise and may not meet with some of the species 

 in flower, the utility of Mr. Lushington's work is apparent. 



Babu Upendranath Kanjilal, of the Indian Forest Depart- 

 ment, has just published a most excellent and handy volume on 

 the local forest flora of the School Circle, North-West Provinces 

 of India, where the forests range in altitude from 1000 to 

 10,000 feet above sea-level. This work is also referred to in 

 the February number of the Indian Forester, in which is also 

 found a list, systematically arranged, of trees and shrubs in the 

 Jerruck division of Sind, by Mr. G. K. Betham, of the Indian 

 Forest Department. 



Any habitual reader of the Indian Forester will see that 

 Indian forest officers pay considerable attention to biology, 

 chiefly as regards plants and insects ; but, after all, their chief 

 duty is the economic management of the Indian forests, and 

 the great amount of work this involves and its value to the 

 Indian Empire can be appreciated only by those who have 

 given a fair attention to forestry in all its bearings. 



Besides British India and the included and adjoining native 

 States, such as Cashmere, Indian foresters are now employed 

 in Siam, the Phili]ipine Islands, Cape Colony and the Sudan. 

 Owing to the great devastation of woodlands in the Transvaal 

 and Orange River Colonies, which is graphically described in a 

 recent number of the Kei'tie des Eaiix et Forcts (the French 

 Forestry Magazine), it is to be hoped that a sound administra- 

 tion of forestry may soon be established in these territories. 



Coopers Hill, February 24. W. R. Fisher. 



Cherry Disease. 



SIy attention has just been called to a letter in your issue of 

 January 30 from Sir W. T. Thiselton-Dyer, which gives the 

 strongest possible confirmation to my contention that a fully 

 equipped State Agricultural Laboratory is a national desider- 

 atum, and that in this respect Britain is behind other countries. 



Vour correspondent implies in his letter that with Kew and 



NO. 1688, VOL, 65] 



the British Museum in existence there is no pressing need for 

 any other institution. The Director's letter proceeds to relate 

 what Kew has done " promptly and in ordinary routine" for 

 the protection of the British farmer against the cherry disease ; 

 and the sum of it is that in November, 1900, Kew answered an 

 inquiry from Mr. A. O. Walker by telling him that the fungus 

 on the cherry leaves sent by him was Gnomonia erythtostoma. 

 The next step taken by Kew — and the only public one — is the 

 director's ungenerous criticism of what has been done meanwhile 

 by the Royal Agricultural Society. (Mr. Walker's letter to the 

 Gardeners' Clironicle in May, 1 900, was apparently his own 

 private action, in no way initiated by Kew, and was certainly 

 not an official step.) 



A pathogenic fungus can be named at any time in ordinary 

 routine for an individual inquirer either at Kew or at the 

 British Museum ; but this is the smallest part of the work of a 

 State Agricultural Laboratory. 



The Royal Agricultural Society of England, which — public- 

 spirited though it be — is not a State-suppotted institution, took 

 some practical steps. It was not until December 1900 that a 

 specimen of the cherry disease was received at the laboratory 

 of that Society, and at the next council meeting on February 

 5, 1901, I reported on the disease. This report was published 

 in the agricultural papers of that and the following weeks, and 

 was widely distributed in leaflet form by the Society among the 

 Kent cherry-growers, to its own members and to non-members 

 indiscriminately. A conference with the cherry-growers at 

 Maidstone followed, and the result has been that the disease 

 was carefully observed, and sufficient information reached the 

 Society's laboratory to enable the publication in its /fl«rHa/ of a 

 detailed account of the disease as it has appeared in England. 

 I regret to add that I have received specimens of wild cherry 

 from Somerset attacked by the Gnomonia. 



Any benefit which may conceivably have come to the British 

 farmer from Kew in this matter accrued indirectly in May through 

 the action of a private individual. The Royal Agricultural 

 Society had already in February taken the valuable practical 

 steps which in most other countries would have been the duty 

 of a State Agricultural Laboratory. 



I need not trouble you in regard to your correspondent's kind 

 correction oi an intentionally indefinite description in my report, 

 which has been put right in its final form, issued ten days before 

 his letter was published ; nor with his other criticisms upon 

 your report of the meeting of the Royal Microscopical Society, 

 criticisms which to an intelligent and careful reader answer 

 themselves. Willia.m Carruthers. 



44 Central Hill, Norwood, February 22. 



Mr. Carruthers' letter is open to some criticism. Taking 

 it, however, as it stands, it proves conclusively that in the case 

 of the cherry-leaf disease everything has been done by exist- 

 ing agencies that was practically possible. This particular 

 instance therefore [aflbrds no basis for the demand for a Slate 

 Agricultural Laboratory. 



As I have already stated, the disease does not appear to have 

 been brought under the notice of the Board of Agriculture. 

 Had it been so, that department, if it had seemed desirable, 

 could have relieved the Royal Agricultural Society of the task 

 of preparing and distributing a leaflet. Mr. Walker, however, 

 points out in Nature for February 6 (p. 318) that " the 

 disease has almost disappeared, though no preventive measures 

 such as stripping the leaves were taken." 



The object of my letter was to make a protest against the 

 present tendency to demand fresh State machinery instead of 

 endeavouring to increase the usefulness of that which already 

 exists. W. T. Thiselton-Dyer. 



Kew, February 26. 



Identity of Negative Ions Produced in Various Ways. 



From the results of some experiments which I have recently 

 made, it can be shown that the negative ions produced in various 

 gases by Rontgen rays, or by collision, are all identically the 

 same and are smaller than the molecules of hydrogen. 



The following results have been established by the researches 

 on this subject which have been already published (J. S. 

 Townsend, Pliil. Mag., February 1901 ; J. S. Townsend and 

 P. J. Kirkby, Phil. Mag., June 1901 ; P. J. Kirkby, Phil. 

 Mag., February 1902) : — 



[a) The negative ions produced in a gas by Rontgen rays 



