May, 1915. 



KNOWLEDGE. 



137 



to produce experimentally a variety or strain of 

 some of them which is capable of attacking a second 

 plant, by injecting the juices of the first into the 

 tissues of the second. After several generations of 

 this treatment the fungus has been rendered capable 

 of attacking the second host directly. Massee 

 has also experimentally induced a saprophytic 

 fungus to become parasitic. Trichothecium cand.id.um 

 is only found in nature growing on dead substances. 

 But by injecting sugar into the leaves of a Begonia 

 this fungus has been induced to attack the plant, 

 grow on it, and produce normal spores. Spores of 

 the second generation were sown on another Begonia 

 plant in exactly the same manner, except that less 

 sugar was injected into its leaves, and the experi- 

 ment was continued until, after twelve generations, 

 a strain of Trichothecium was produced capable of 

 infecting a Begonia leaf directly without the pre- 

 vious injection of any sugar at all. It has also been 

 shown that plants normally immune to infection by 

 certain fungi may become susceptible if they are 

 first injured. It is probable that a good many fungi 

 which are found growing on living trees usually 

 obtain a footing in the tissues of the tree by attack- 

 ing a branch injured by wind or storm. The beech- 

 tuft (Armillaria mucida) (see Figures 118 and 122) 

 — a beautiful ivory-white toadstool found growing 

 on living beech trees, often in great abundance — 

 is an instance of this. All appearances indicate 

 that it is definitely parasitic in nature ; but, though 



Fischer was able to cultivate it from its spores, 

 and get it to produce fructifications while growing 

 on sterilised bread and beech wood, all attempts 

 which he made to infect living beech trees failed 

 entirely. Probably in nature the fungus only grows 

 on beech trees which have been prepared for it by 

 the growth of some other fungus, or it may be that 

 it starts growth as a saprophyte on some dead 

 branch, and then obtains sufficient vigour to attack 

 the living parts of the tree. 



There appears to be no doubt at all that Fomcs 

 annosus (see Figure 120) is a true parasite on living 

 trees. The mycelium is found between the wood 

 and the bark of the roots and lower part of the 

 stem in fir trees as a layer of fine, silky threads, 

 which can be seen through a crack in the bark 

 bulging outward. The mycelium secretes a fer- 

 ment which dissolves out the lignin from the wood 

 of the lower part of the trunk of the tree, and in 

 time makes it hollow ; indeed, foresters are able 

 to recognise the presence of the parasite before 

 any great change takes place in the general nutrition 

 of the tree by the hollow sound produced when the 

 tree is struck. The fructifications of the fungus, 

 which take the form of somewhat irregularly 

 shaped projections composed of masses of fine, 

 vertical tubes open below, are generally borne 

 on the exposed roots of the infected trees, and are 

 often seen where the roots have been laid bare by 

 the burrows of foxes and rabbits. 



(To be continued.) 



SCIENCE IN THE DAILY PRESS. 



Recently Professor R. A. Gregory, the Assistant Editor 

 of Nature, read a paper before the Circle of Scientific, 

 Technical, and Commercial Journalists, in which he con- 

 sidered the accuracy of statements which appear in the 

 newspapers and weekly periodicals, and discussed literary 

 and scientific writers, as well as some public beliefs which 

 have been shown to be erroneous. He said : " It is scarcely 

 too much to say that, omitting signed articles written by 

 experts, few newspapers make any announcement relating 

 to a scientific subject without committing a mistake. Either 

 terms are wrongly used, or a matter of common knowledge 

 among men of science is regarded as a remarkable discovery, 

 or observations of a sensational kind are presented to the 

 public as if they were established truths, though they 

 await confirmation from the scientific world, and are mostly 

 unworthy of serious consideration. 



" It seems to be too much to expect literary people to 

 possess an elementary knowledge of science, or to have any 

 sympathy with scientific precision, but it is not unreasonable 

 to ask for accuracy of description when they are dealing 

 with natural facts and phenomena. 



" We are often told that men of science should cultivate 

 the art of literary expression, but the stronger necessity for 

 literary men to have at least a nodding acquaintance with 

 the outstanding facts of natural knowledge is overlooked. 

 The first business of the man of science is to create new 

 knowledge, and not necessarily to clothe his discoveries 

 in a pleasing dress, though he may do so." 



Two examples were given by Professor Gregory where 

 scientific enquiry had failed to support popular opinion. 

 One was alleged change of climate, and the other the con- 



nection between the Moon and the weather. When meteor- 

 ological records are examined they show that the temper- 

 ature, rain, frost, and so on, are much the same at the 

 present time as they were in the early days of the declining 

 generation. Moreover, " from an examination of old records, 

 and of the long series of observations made at Greenwich. 

 Sir John Moore was able to show to the British Association, 

 in 1908, that no appreciable change has taken place in 

 the climate of the British Isles during the past six 

 cent unes. 



"The only definite association that can be regarded as 

 established between changes ol the Moon and weather 

 is that thunderstorms are slightly more frequent near New 

 Moon and the First Quarter than near Full Moon and the 

 Last Quarter ; and it is noteworthy that this is overlooked 

 completely in proverbial philosophy." 



Other fallacies touched upon were that the noise of guns 

 causes ram, that there is ll.une from a volcano, and living 

 toads and ln>gs are found in blocks oi coal and other rock, 

 or that there is such a thing as a thunderbolt. 



With regard to the last part of his subject, Professor 

 Gregory said that " the public likes to believe that men of 

 science predicted from theory that this or that thing was 

 impossible whit h \v. is afterwards achieved ; and its literary 

 guides usually associate a great discovery, not with the man 

 whose work in the laboratory oi study led to it. but to the 

 man who made a commercial success of it. It was the 

 mathematical work of Clerk Maxwell and the scientific 

 experiments of lleitz which produced wireless telegraphy. 

 but to the popular press the only man responsible for this 

 wonderful discovery is Mr. Marconi." 



