September 9, 1897] 



NATURE 



459 



are now known to be very common in plants, and the suspicion 

 that fungi do much of their work with their aid is abundantly 

 confirmed. 



Payen and Persoz discovered diastase in malt extract in 1833, 

 and in 1836 Schwann discovered peptase in the juices of the 

 animal stomach. Since that time several other enzymes have 

 been found in both plants and animals, and the methods for 

 extracting them and for estimating their actions have been much 

 improved, a province in which Horace Brown, Green, and 

 \'ines have contributed results. 



It seems not improbable that there exists a whole series of 

 these enzymes which have the power of carrying over oxygen 

 to other bodies, and so bringing about oxidations of a peculiar 

 character. These curious bodies were first observed owing to 

 studies on the changes which wine and plant juices undergo 

 when exposed to the action of the oxygen of the air. 



In the case of the wine certain changes in the colour and 

 taste were traced to conditions which involved the assumption 

 that some body, not a living organism, acts as an oxygen- 

 carrier, and the activity of which could be destroyed by 

 heating and antiseptics. It was found that similar changes 

 in colour and taste could be artificially produced by the 

 action of ozone, or by passing an electric current through 

 the new wine ; indeed, it is alleged that the ageing of wine 

 can be successfully imitated by these devices, and is actually 

 a commercial process. 



The browning of cut or broken apples is now shown to be due 

 to the action of a similar oxydase — i.e. an oxygen-carrying 

 ferment, and the same is claimed for the deep-colouring of 

 certain lacks, or lackers, obtained from the juice of plants such 

 as the AnacardiacetB, which are pale and transparent when 

 fresh drawn, but gradually darken in colour on exposure to air, 

 Bertrand found in these juices an oxydase, which he terms 

 laccase, and which affects the oxygen-carrying, and converts the 

 pale fluid juice to a hard dark brown varnish. 



Other oxydases have been isolated from beets, dahlia, potato- 

 tubers, and several other plants. 



These discoveries led Bourquelot and Bertrand in 1895 to the 

 explanation of a phenomenon long known to botanists, and 

 partly explained by Schonbein as far back as 1868. If certain 

 Fungi (e.g. Boletus liiridus) are broken or bruised, the yellow 

 or white flesh at once turns blue : the action is now traced to 

 the presence in the cell-sap of an oxydase, the existence of which 

 had been suspected but not proved, and the observers named 

 assert that many fungi (59 out of 107 species examined) contain 

 such oxydases. 



It will be interesting to see how far future investigations sup- 

 port or refute the suggestion that many of the colour-changes in 

 diseased tissues of plants attacked by fungi are due to the action 

 of such oxydases. 



Wortmann, in 1882, showed that bacteria, which are capable 

 of secreting diastase, can be made to desist from secreting this 

 enzyme if a sufficient supply of sugar be given them, and 

 since then several instances have been discovered where fungi and 

 bacteria show changes in their enzyme actions according to the 

 nature of their food supply. Nor is this confined to fungi. 

 Brown and Morris, in 1892, gave evidence for the same in the 

 seedlings of grasses : as the sugar increased, the production of 

 diastase diminished. 



It is the diastatic activity of Aspergillus which is utilised in 

 the making of sake from rice in Japan, and in the preparation of 

 soy from the soja-bean in the same country, and a patented pro- 

 cess for obtaining diastase by this means exists ; and Katz has 

 recently tested the diastatic activity of this fungus, of Penicil- 

 liuvi, and of Bacterium magatheriuni in the presence of large 

 and small quantities of sugar. All three organisms are able to 

 produce not only diastase, but also other enzymes, and the 

 author named has shown that as the sugar accumulates the 

 diastase formed diminishes, whereas the accumulation of other 

 carbo-hydrates produces no such effect. 



Hartig's beautiful work on the destruction of timber by fungi 

 obtains new interest from Bourquelot's discovery of an emulsion- 

 like enzyme in many such wood-destroying forms. This enzyme 

 splits the Glucosides, Amygdalin, Salicin, Coniferin, &c., into 

 sugars and other bodies, and the hyphae feed on the carbo- 

 hydrates. I purpose to recur to this subject in a communica- 

 tion to this Section. The fact that Aspergillus can form invertins 

 of the sucrase, maltase, and trehalase types, as well as emulsin, 

 inulase, diastase, or trypsin, according to circumstances of 

 nutrition, will explain why this fungus can grow on almost any 



organic substratum it alights on, and other examples of the same 

 kind are now coming to hand. 



The secretion of special enzymes by fungi has a peculiar interest 

 just now, for recent investigations promise to bring us much 

 nearer to an understanding of the phenomena of parasitism than 

 we could hope to attain a few years ago. 



De Bary long ago pointed out that when the infecting germinal 

 tube of a fungus enters a plant-cell, two phenomena must be 

 taken into account, the penetration of the cell-walls and tissues, 

 and the attraction which causes the tips of the growing hypha 

 to face and penetrate these obstacles, instead of gliding over 

 them in the lines of apparent least resistance. 



The further development of these two themes has been 

 steady and unobtrusive, and from various quite unexpected 

 directions more light has been obtained, so that we are now in 

 a position to see pretty clearly what are the principal factors 

 involved in the successful attack of a parasitic plant on its 

 victim or "host." That fungi can excrete cellulose-dissolving 

 enzymes is now well known, and that they can produce enzymes 

 which destroy lignin must be inferred from the solution of wood- 

 cells and other lignified elements by tree-destroying fungi. 

 Zopf has collected several examples of fungi which consume 

 fats, and further cases are cited by Schmidt, by Ritthausen, 

 and Baumann. In these cases also there can be no doubt that 

 an enzyme or similar body is concerned. 



There is one connection in which recent observations on 

 enzymes in the plant-cell promise to be of importance in ex- 

 plaining the remarkable destructive action of certain rays of 

 the solar-light on bacteria. As you are aware, the English 

 observers Downes and Blunt showed long ago that if bacteria 

 in a nutrient liquid are exposed to sunlight, they are rapidly 

 killed. Further researches, in which I have had some part, 

 gradually brought out the facts that it is really the light rays 

 and not high temperatures which exert this bactericidal action, 

 and by means of a powerful spectrum and apparatus furnished 

 by the kindness of Prof. Oliver Lodge I was able to obtain 

 conclusive proof that it is especially the blue-violet and ultra- 

 violet rays which are most effective. This proof depended on 

 the production of actual photographs in bacteria of the spectrum 

 itself. Apart from this, I had also demonstrated that just such 

 spores as those of anthrax, at the same time pathogenic and 

 highly resistent to heat, succumb readily to the action of these 

 cold light-rays, and that under conditions which preclude their 

 being poisoned by a liquid bathing them. 



The work of Brown and Morris on the daily variations of 

 diastatic enzyme in living leaves, and especially Green's recent 

 work on the destructive action of light on this enzyme, point to 

 the probability that it is the destruction of the enzymes with 

 which the bacterial cells abound which brings about the death of 

 the cell. 



That these matters' are of importance in limiting the life of 

 bacteria in our streets and rivers, and that the sun is our most 

 powerful scavenger, has been shown by others as well as myself. 

 In this connection may also be mentioned Martinand's observa- 

 tions, that the yeasts necessary for wine- making are deficient in 

 numbers and power on grapes exposed to intense light, and he 

 explains the better results in Central France as contrasted with 

 those in the South as largely due to this fact. Whether, or how 

 far, the curious effects of too intense illumination in high lati- 

 tudes and altitudes on plants which might be expected to grow 

 normally there, can be explained by a destructive light action 

 on the enzyme of the leaves, has not, so far as I know, been 

 tested ; but Green's experiments certainly .seem to me to point 

 to the possibility of this, as do the previous experiments with 

 screens of Pick, Johow, myself, and others. 



It is interesting to note that Wittlin and others have con- 

 firmed the conclusion my own few trials with Rontgen rays led 

 to ; they show no action whatever. 



That branch of mycology which is now looked upon by so 

 many as a separate department of science, usually termed bac- 

 teriology, only took shape in the years 1875-79, when its founder, 

 the veteran botanist Cohn, who recognised that the protoplasm 

 of plants corresf)onded to the animal sarcode, and who has been 

 recently honoured by our Royal Society, published his exact 

 studies of these minute organisms, and prepared the way for the 

 specialists who followed. 



It is quite true that isolated studies and observations on 

 bacteria had been made from time to time by earlier workers 

 than Cohn, though it is usually overlooked that Cohn's first 

 paper on Bacteria was published in 1853. Ehrenberg in 



NO. 1454- VOL. 56] 



