i8 



NATURE 



[November 7, 1895 



A DESTRUCTIVE PLANT PARASITE} 



A DISEASE of vine-leaves, characterised by the presence of 

 -'*■ brown or blackish blotches, which frequently spread over 

 the entire surface of the leaf, has been known in European and 

 American vine-growing districts under various provincial names 

 for some years. This disease, known in France as brtmissure, 

 was investigated by Viala and Sauvageau, who concluded that it 

 was due to the presence of a parasitic organism to which the 

 name Plasinodiopkora vitis was given. Prof. Debray's researches 

 show that brunissure is far more generally distributed than was 

 hitherto suspected, having been detected by this observer in 

 plants belonging to forty-two natural orders. In like manner, 

 the leaf is not the part most frequently attacked, as supposed by 

 Viala, Init root, branch, flower, and in fact every portion of a 

 plant is liable to attack. Owing to the absence of spore-forma- 

 tion, zoospores, nuclei, and slender pseudopodia, coupled with 

 the fact that, although a parasite, there is no trace of malforma- 

 tion of the host, Debray considers that the organism under con- 

 sideration cannot be included in the Plasmodiophorce, nor in any 

 other recognised family, and proposes for its reception a new 

 family, Pseudocommideae, and a new genus, Pseudocoininis , 

 allied to Vampyrelloe and Myxomycetse. The supposed or- 

 ganism when in plant cells is difficult to distinguish from the 

 protoplasm of the cell, and more especially the nucleus ; it is, 

 however, more refringent, and usually remains intact after the 

 protoplasm has been destroyed by the use of eau de Javelle. 

 Iodine-green and methylene-blue give a green and blue stain 

 respectively ; the most certain reaction, however, is said to be 

 chlor-iodide of zinc, which gives a yellow or brown colouration 

 to the Plasmodia. The organism is met with under various 

 forms in the cells of the host, never occurring in the intercellular 

 spaces ; the plasmodium may be intimately mixed with, and 

 almost indistinguishable from the protoplasm of the cell, or dis- 

 tinct from the cell-contents and densely vacuolate, or finally, in 

 assuming a spherical form, perfectly homogeneous, or with a few 

 spherical vacuoles. Under certain conditions the plasmodium 

 travels from the interior of the cells of the leaf or other part of 

 the plant to the surface, where it appears as a slimy or gummy 

 secretion, and by this means passes on to other parts of the 

 plant which are attacked. Sometimes the external plasmodium 

 becomes hardened into wax-like masses or cysts, which are con- 

 sidered to represent a resting-stage. The appearance and spread 

 of the disease is much influenced by meteorological conditions, 

 a sudden chill favouring its development. No preventive based 

 on experiment is given, but it is suggested that badly diseased 

 parts should be removed, and the external migration of the 

 parasite checked by a dusting of powdered lime. 



If Debray's ^observations prove to be correct, we have in 

 Pseudoconimis the most universally difiiised and destructive of 

 plant parasites hitherto known. 



SCIENCE IN THE MAGAZINES. 

 ■pVERY individual, as Prof. Milnes Marshall used to say, 

 -"-^ climbs up his own genealogical tree. Embryology shows 

 how human lineaments are developed from a widely typical 

 animal form, and evidences of the same relationship can be 

 obtained from the study of the infant after birth. In the Fort- 

 nightly, Prof. Sully pleads for such study. " Ours is a scien- 

 tific age," remarks he, "and science has cast its inquisitive eye 

 on the infant. We want to know what happens in the first 

 all-decisive two or three years of human life, by what steps 

 exactly the wee amorphous thing takes shape and bulk, both 

 physically and mentally. And we can now speak of the begin- 

 ning of a careful and methodical investigation of child nature 

 by men trained in scientific observation. This line of inquiry, 

 started by physicians, as the German Sigismund, in connection 

 with their special professional aims, has been carried on by a 

 number of fathers and others having access to the infant, among 

 whom it may be enough to name Darwin and Preyer." The 

 biologist is able to use the physical development of a child to 

 show man's kinship to the lower animal world, and the develop- 

 ment of an infant's mind indicates to the psychologist how the 

 mental history of the race has been evolved. It does not need 

 a very acute observer to see the intellectual and moral resem- 

 blances between the lowest existing races of mankind and 



^ " La Brunissure chez les v^g^taux," Rez'ue de Viticulture, 5 Rue Gay- 

 Lussac. 



NO. 1358. VOL. 53] 



children. Several anthropologists have studied this phase of 

 child-life, and have found it full of interest. The difficulty is 

 to get systematic and scientific observations of children. Prof, 

 Sully shows that the work is worth doing, and indicates some 

 of the lines of study to be followed ; all that is needed is 

 methodical and trustworthy registration of the successive stages 

 in the child's development. 



A second article in the Fortnightly is a reply by Prof. Karl 

 Pearson to an article in the September number of the Review, 

 where Dr. St. George Mivart attempted to describe the limits 

 of scientific knowledge and inquiry, and to show that many 

 teachers of science were dogmatic, or "denominational," as he 

 called it. Two other articles in which some of our readers may 

 find interest are "Brahminism and the Foundations of Belief," 

 by Vamadeo Shastri, and "Vegetarianism," by Mr. T. P. 

 Smith. 



An article on Pasteur, contributed by Profs. Patrick Geddes 

 and J. A. Thomson to the Contemporary, is a readable and fairly 

 full statement of his personal life and scientific work. The 

 authors thus sum up Pasteur's legacy to the world : "There is 

 the impulse which he gave, after the successful organisation of 

 his own Institute, to the establishment in other countries of 

 similar laboratories of preventive medicine, and, one may also 

 say, of experimental evolution. There is his educative work at 

 Strassburg and Lille, at the ^fecole Normale and the Sorbonne, 

 and, above all, in the smaller yet world-wide circle of his im- 

 mediate disciples. To general biology his chief contribution 

 has been the demonstration of the part which bacteria play, not 

 only in pathological and physiological processes, but in the wider 

 drama of evolution. To the chemist he has given a new theory 

 of fermentation ; to the physician, many a suggestive lesson in 

 the etiology of diseases ; and a series of bold experiments in 

 preventive and curative inoculation, of which Roux's treatment 

 of diphtheria, and Prof. Eraser's new remedy for snake-bites, 

 are examples at present before the public ; to the surgeon, a 

 stable foundation, as Lister acknowledged, for antiseptic treat- 

 ment ; to the hygienist, a multitude of practical suggestions con- 

 cerning water-supply and drainage, disinfection and burial. On 

 brewer, distiller, and wine-maker he has forced the microscope 

 and its results ; and he has shown both agriculturist and stock- 

 breeder how some, at least, of their many more than ten plagues 

 may be either averted or alleviated." In the same Review Mr. 

 Herbert Spencer traces the development of the judge and lawyer, 

 and points out the relations between the priestly and judicial 

 functions. There is also a forcible and philosophical reply by 

 Father Tyrrell to Miss Cobbe's utterances in the October number. 

 We content ourselves with giving two of the thirteen points upon 

 which Father Tyrrell bases his position ; they are : ( i ) as 

 animals vary in sensibihty, our duties concerning them vary also ; 

 (2) in the abstract, vivisection is not only permissible but 

 laudable in certain conditions. Whether these conditions are 

 or can be realised is a matter of opinion. He concludes : 

 " Whatever one may think of the old-fashioned psychology on 

 which this system rests, no one can deny that it is at least 

 coherent and in keeping with the common sense of the best part 

 of mankind, and that it offers a full and firm basis for a humane 

 and reasonable treatment of animals, without entailing any of 

 those hopeless problems which Miss Cobbe has to encounter in 

 the application of her system." 



A fine portrait of the late Prof, von Helmboltz, taken on the 

 day of his last appearance in the lecture room, by C. Riborg 

 Mann, appears in Scribner, accompanied by a brief summary of 

 his leading contributions to science. The circumstances under 

 which the photograph was taken are thus stated by the author : 

 "At the close of his lecture on Saturday, July 7, 1894, Prof, 

 von Helmholtz, at my earnest request, remained a few minutes 

 in the class room and allowed me to photograph him. He stands 

 as he was accustomed to appear before his students, the formulas 

 as he had just written them remaining on the blackboard as a 

 suitable background. By a strange working of fate, that was 

 the last day on which he lectured, excepting one, when he gave 

 some matter supplementary to this occasion ; and this is his last 

 photograph." A paper entitled "The Logic of Mental 

 Telegraphy," contri'outed by Prof. Joseph Jastrow to the same 

 magazine, should be taken to heart by a gullible public. 

 Nothing is said about the attempted experimental tests of 

 thought-transference, which may be worth investigation, but it is 

 shown that coincidences will account for the possibilities of 

 mental telegraphy believed in by the popular mind. 



A few reminiscences of Huxley's habits and work at the 



