740 



NATURE 



[NOVEMBK 



V- J 



sulphate applied to acid «ioU cauRetl a decrease iii 

 crop, whereas if calcium carbonate was applied in 

 addition to neutrali.Hc the acidity, increasea yields 

 were < Soluble salts of manganese in acid 



soils t fore be one of the causes of toxicity 



in sutti sous as exhibit toxic effects, an excess of 

 manganese sulphate rendering a soil more or less 

 sterile with respect to the growth of plants. 



Silver-leap Disease. — The fourth of the series of 

 papers on this subject by Mr. F. T. Brooks and his 

 co-workers appears in the Journal of Pomology, Vol. 

 iii.. No. 3, September. With financial aid from the 

 Ministry of Agriculture, these important investiga- 

 tions are extending in scope, and besides experiments 

 at Cambridge and at the John Innes Horticultural 

 Institution, Merton, work has been done upon orchard 

 trees at the East Mailing Fruit Research Station and 

 at Heston, Middlesex. The parasitic fungus Stereum 

 purpureum is responsible for the typical silver-leaf 

 disease, and in this fourth report. Brooks and H. H. 

 Storey criticise Bintner's recent attempt to distin- 

 guish a false " silver-leaf " disease due to other 

 physiological causes while pointing out that the 

 silver\' appearance, due usually to the optical effects 

 produced by an afr gap between leaf epidermis and 

 mesophyll, may frequently arise from accidental dis- 

 turbances quite unconnected with the entry of 

 Stereum purpureum. The experiments now recorded 

 show that the fungus readily infects the living wood 

 at any exf>osed surface, penetrating such tissues more 

 readily than shoots previously killed in the autoclave, 

 in which it seems to be less active than many sapro- 

 phytic moulds. A very interesting description is 

 given of the conditions found in Pershore plums which 

 had been infected by the disease and then " grew out " 

 of it. On examination the dead fungus patches 

 could be seen in the wood sharply delimited from the 

 healthy tissues by a band of gum excreted from the 

 tissues. The accumulation of these gum-like sub- 

 stances both in diseased tissues and at the surface of 

 a healthy wound are obviously profitable subjects for 

 further study. Brooks and Storey record many 

 observations on natural wound protection in fruit 

 trees and upon the usual dressings applied to protect 

 such wounds ; in their experience gas tar has been 

 the most valuable dressing, Stockholm tar proving 

 very disappointing as a means of protecting wounds 

 against fungal attack. 



Dissecting a Devonian Fish. — A paljeontologist 

 of our acquaintance is wont to dream of finding a 

 palaeozoic fossil with all its soft parts so beautifully 

 preserved that he can dissect them. Our friend will 

 be envious when he reads in the annual report of the 

 Field Museum of Natural History (Chicago, 1923) how 

 Dr. Erik Stensio, the new head of the Palaeontological 

 Department of the Swedish State Museum, spent ten 

 days at Chicago dissecting the head of a Devonian 

 fish, Macropetalichthys. This specimen, it is said, 

 allowed Dr. Stensio to obtain an exact knowledge of 

 the shape of the brain and details of the nervous and 

 circulatory system of the head. These facts might 

 possibly have been inferred from the petrified skeletal 

 tissues ; but the report says precisely : " The pre- 

 servation of these soft parts was so perfect that they 

 could be studied almost as well as if it were a fresh 

 specimen." The specimen has been mounted for 

 museum exhibition in such a way as to make a 

 complete whole with all the dissect^ parts visible, 

 and with every portion removable for close study. 

 Zoologists will await with interest the publication of 

 Dr. Stensio's memoir. 



Free Radicles.— J. B. Conant and A. W. Sloan 

 have recently published a preliminarj' paper on the 



NO. 2820, VOL. I 12] 



formation of free radicles (J, Amcr. Chem. So< . s 

 45, p. 2466). The reduction of triphenylp^ 

 chloride with vanadous chloride yields a : 

 substance which is insoluble in water and hi 

 as a free radicle. The same reducing agf»nt r- ' ;i . 

 triphcnylcarbinol in concentrated ) 

 sulphuric acid solution to free triphen 



Cellulose Derivatives. — The technology of cell. 

 lose derivatives is discussed in an article in tl.. 

 Chemical Trade Journal lot October 19, which ; 

 mainly devoted to the newer ethers and esters. '11 

 preparation of cellulose butyrates is receiving attct 

 tion, because by introducing more conw.l.v .. 

 radicals it is hoped to prepare esters 

 solubility properties. The interest in 1 

 ethers has directed attention to impr 

 manufacture of diethyl sulphate, these 

 in the article. The properties of the variou-^ 

 and ethers are given. 



Preservation of Wood. — ^The Chemical Trail 

 Journal for Oct. 5 contains an article on wood pr< 

 servatives. The art of wood preservation dates ba. V. 

 from very early times; it was practised I- • 

 Egyptians, who used anti-septic oils for the p 

 Burnett in 1838 introduced the use of zinc cli 

 Wolman in 1906 patented the use of certain ll 

 in conjunction with other salts, and from th: 

 "hundreds of patents on the subject have been taken out 

 In recent times the creosoting process has been iiitr. 

 duced, but it confers odour and infiammabilit\ 

 timber. The methods of impregnation are dV 

 in the article, and the results obtained from the uses oi 

 various salts are described. A note is also arirlrrl on th.- 

 preservation of wood pulp. 



Magnetic Declination at Jm.w — .\ 

 detailed study by Dr. C. Chree, of the " Absolut 

 range of magnetic declination at Kew Obser\ 

 Richmond, 1858 to 1900," has just been pu! 

 in the Geophysical Memoirs (vol. iii. No. 22) o; l..^ 

 Meteorological Office. The annual variation of the 

 daily range is examined by subdividing the year into 

 73 five-day periods ; for each group of five daN'S the 

 4 2 -year mean daily range is given, also the largest and 

 least values ; smoothed means are given also for 

 years of sunspot maximum and minimum. Tht- 

 remges are, of course, distinctly less in minimum than 

 in maximum sunspot years. The daily range under 

 goes a double oscillation in the course of a year, with 

 majcima at the equinoxes and minima near the solstices 

 Again, Wolf's linear relation, R=a-|-6S, connectin;; 

 the range R with the sunspot number S, is examined : 

 a and b are found to var)' quite considerably both 

 throughout the year and from one year to another. 

 The determination of a and 6 does not in itself give 

 a measure of the degree of correlation between R and S. 

 and this question is separately investigated. The 

 mean correlation coefficient for the whole p>eriod is 

 0-86, but in the mean of the winters it is only 0-53. 

 while there are conspicuous variations in the results 

 for the four groups of years, each roughly comprising 

 one sunspot period, into which the whole series is 

 divided. Interesting frequency tables are also given 

 (a) showing the distribution of ranges of different 

 sizes, in each individual year, for the said four groups 

 of years, for sunspot maximum and minimum years, 

 and for each month of the year ; and [b) showing the 

 distribution of the hour of daily maximum and 

 minimum declination for similar groups of the data. 

 The paper contains a large amount of imp>ortant 

 though technical information ; the results would be 

 more readily comprehended if they had been indicated 

 by graphs based on the numerous tables. 



