620 



NA TURE 



[April 26, 1906 



found to exhibit a very strong emission band at 4 75 \i. 

 The emission spectrum of C,H 5 OH shows that a vapour 

 in a vacuum tube can emit a continuous spectrum. 



Angstrom's conclusions — deduced from the fact that the 

 total radiation increases, while the luminous radiation 

 decreases, with increase of pressure in the gas — that there 

 are two kinds of radiation present during the electrical dis- 

 charge are found to be in close agreement with the observed 

 facts. These different discharges were named " regular " 

 and " irregular " [i.e. luminescence) by the previous 

 observer. An interesting theoretical discussion of the 

 action of pressure in this connection is given in the volume. 



W. E. R. 



DISEASES OF VINES. 1 



TWO parts of the Annates de I'lnstitut Central Ampelo- 

 logique Royal Hongrois, devoted to two of the vine 

 diseases, have lately reached us. 



In one of these parts (part iii.) an account is given of 

 the little known disease caused by the attacks of Phyllo- 

 sticta Bizzozeriana. The disease was first noticed in the 

 year 1900, and it has been kept under observation since 

 then, with the result that its spread has been traced in some 

 detail. The symptoms are somewhat similar to those of 

 the dreaded "black-rot," but it does not appear as if it 

 will prove so dangerous a parasite. In addition to a brief 

 life-history of the fungus, illustrated by an excellent plate, 

 a useful compendium of the species of Phyllosticta occurring 

 or. Ihe vine is given. 



Part iv. contains an unusually complete account of the 

 " grey-rot " caused by Botrytis cinerea. This is one of 

 the parasites of the vine which the cultivator most dreads. 

 All aerial parts of the host-plant are attacked indis- 

 criminately, and quickly become covered with a greyish 

 or brown mould, which produces enormous quantitii s of 

 ashy-grey spores. This stage is succeeded by the form- 

 ation of small black sclerotia in the diseased tissues of the 

 -hnis, leaves, and fruits. Naturally the fungus has been 

 investigated time after time, but the researches of Istvanffi, 

 published in this volume, have added a number of fresh 

 facts to our knowledge of its life-history. In tin- first 

 place, a series of laboratory investigations was made with 

 the object of determining the conditions under which the 

 fungus brought about the infection of the host-plant. The 

 optimum temperature for the germination of the spores 

 proved to be 25 C, whilst the spores were killed by ex- 

 posure to a temperature of 38 C. to 41 C. The effects 

 of drying the spores were then investigated. Oni day's 

 drying over sulphuric acid at laboratory temperatures, either 

 in light or darkness, was sufficient to kill 75 per cent, of the 

 spores, and desiccation lor thirty-six clays was fatal to all 

 of them. Spores previously germinated and exposed to 

 this treatment suffered still more severely. The results of 

 freezing were again seriously to diminish their germinating 

 capacity. 



The action of a number of the commoner fungicides 

 on spores was then examined, with interesting results. 

 Thus a 1 per cent, solution of Bordeaux mixture only 

 prevented the germination of some 60 per cent., and a 

 10 per cent, solution about 10 per cent. Spores which 

 were allowed to dry after soaking in Bordeaux mixture all 

 failed to germinate. Others sown in drops on the foliage 

 of the host-plant not only germinated, but infected the 

 tissues below them. On examining the action of the con- 

 stituents of this mixture, lime water proved to be singu- 

 larly efficacious in preventing germination. 



In the majority of these experiments the spores of 

 Monilia and of Coniothvrium were exposed to the same 

 conditions, with results, on the whole, similar to those 

 already quoted. At the same time, the life-history of the 

 fungus was traced in detail. Istvanffi succeeded in 

 germinating the sclerotia, and has settled the point once 

 for all that they do give rise to the apothecia of Sclero- 

 tinia fuckeliana. So many observers have failed to obtain 

 this ascigerous stage that it is well to have this definite 

 statement. The sclerotia retain their germinating capacity 

 for at least twenty-one months. Another interesting point 



1 "Annates de I'lnstitut Central AmpiHiIogiqiM Royal Hongrois," 

 tome iii., livre 3 and 4, 1905. (Budapest, 1905.) 



NO. 1904, VOL. 73] 



brought out in the course of this research is that the well 

 known adpressoria of the fungus are the early stages in the 

 development of the sclerotia. In addition to the micro- 

 conidia observed by Brefeld and others, Istvanffi records the 

 production of an oidial stage. 



For further details, and for methods to be adopted for 

 checking the spread of this pest, the original must be 

 consulted. It is full of points of interest to the student of 

 plant pathology, and makes one regret more and more 

 that this country possesses no institute similar to the 

 Central Ampelologique Royal Hongrois, where the pressing 

 problems of plant disease can be adequately examined. 

 Here we have to trust to the private individual for what 

 investigations are made, and he all too rarely has oppor- 

 tunities to make them on the comprehensive scale possible 

 at such an institution. 



EARTHQUAKE ORIGINS. 

 A MONG the most interesting and important of the new 

 ■^ ideas, which have been introduced into seismology, in 

 late years, must be classed Major E. G. Harboe's notion of 

 the nature of earthquake origins. Originally treated as a 

 point, the focus of an earthquake has long been recognised 

 as an area, but we are still in the habit of regarding it as 

 restricted in size and small in comparison with the 

 dimensions of the area over which the earthquake is felt. 

 On this hypothesis the decrease in violence is correlated 

 with increase in distance, and due to a gradual diminution 

 of intensity as the disturbance travels from its origin ; 

 according to Major Harloe's conception, the focus of an 

 earthquake is no longer restricted in size, but ramifies, 

 with a varying degree of initial violence, over nearly the 

 whole of the seismic area. 



On the generally accepted hypothesis the coseismal lines 

 should more or less correspond with the isoseismal, a de- 

 crease in violence being accompanied by an increase of 

 time interval, but such is far from being the case, and we 

 have been in the habit of attributing the irregularities to 

 errors of observation ; Major Harboe has now shown that 

 another explanation is possible, and that the irregularities 

 in recorded times almost disappear if his hypothesis of the 

 nature of the origin is adopted. From the discussion id 

 the records of earthquakes he reaches the conclusion that 

 the true rate of propagation of the sensible shock is about 

 04 kilometre per second, the higher velocities obtained by 

 other investigators being compounded of the rate of pro- 

 pagation of the disturbance along the origin, and that of 

 the wave-motion set up by this disturbance. 



This rate of propagation is that of the sensible shock, 

 which can be felt by human beings, and not that of tin- 

 large waves recorded by seismographs outside the seismic 

 area proper ; the latter, the rate of propagation of which 

 is about 3 kilometres per second, are regarded as different 

 in character, and propagated in the consolidated rock at 

 some little depth below the surface, the sensible shock 

 being due to quite superficial waves propagated through 

 the more fissured and less coherent surface rocks. 



One of the weightiest of the objections to this hypothesis 

 was 1 In- value of 328 + 005 km. sec. obtained by Profs. 

 Sekiya and Omori in 1902 from the seismic triangulation 

 started by Prof. Milne in 1884. This is dealt with in 

 vol. viii., part iii., of Gerland's Beitrage zar Geophysik, 

 where Major Harboe remarks that, in spite of the long 

 period over which the observations extended, only four 

 earthquakes seem to have given usable records from all 

 the stations, three earthquakes at three stations, and one 

 at two stations. Taking two of these earthquakes, for 

 which records from a number of meteorological observ- 

 atories have been published, he finds that the velocity and 

 direction of propagation, deduced from the triangulation. 

 lead to most discordant results at other stations, irregulari- 

 ties which disappear if a branch of the origin is supposed 

 to have traversed the field of triangulation and the disturb- 

 ance to have spread outwards to the stations. 



Whether the hypothesis stands the test of future in- 

 vestigation or not, it seems to explain many previously 

 inexplicable anomalies, apart from those of time. It 

 appears to work out satisfactorily in the case of those 

 earthquakes by which Major Harboe has attempted to test 



