433 



JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 



[ December 27, 1877. 



efforts as enables us to enjoy that which I heartily wish every 

 reader of the Journal — 



A Happy New Teae. 

 — Edward Luckhurst. 



POTATO DISEASE. 



With much surprise and some pleasure I have read the 

 articles by "Amateur" on "Speculations as to the Nature 

 and Origin of the Potato Disease." Predisposing influences 

 no doubt there are, but these must not be confounded with the 

 cause of the dieease itself, which it can scarcely be delusion 

 to believe is now clearly attributable to Peronospora infestans, 

 known as the Potato fungus, perhaps not the only one to 

 which it is liable or which may help sometimes to produce the 

 condition of disease. Why should there be any speculation 

 when authorities who investigate bring forward the result of 

 their research ? Further research surely is the only thing 

 admissible on which to form an opinion. The writings of 

 well-known scientific men give evidence of the above cause, 

 and this we must assume to be trustworthy. I cannot recall 

 any investigator who has reached any but this accepted con- 

 clusion. That everybody is not convinced is of no consequence. 

 The subject is of such a nature that few comparatively are in 

 a position to say from immediate observation whether a fungus 

 is the cause or not. There are those who will not or cannot 

 accept an evident fact. A strange doctrine is not easily re- 

 ceived or criticised by those who have no knowledge by which 

 to compare and grasp the new theory or fact. Many absur- 

 dities have come from those who read to no purpose or do not 

 investigate for themselves. The word "investigate" is used in 

 its full meaning. In this ease it implies the use of the micro- 

 scope as a preliminary, an instrument which " Amateur. " does 

 not appear to have used ; yet inclining as he does to the fungus 

 it might, with the help of a little farther experiment, place 

 the matter to his mind beyond the region of speculation, where 

 it is, I believe, to the minds of. the majority of those who are 

 worth attention. 



" Amateub " says that " an able botanist not long ago came 

 out with the astounding statement that everybody was con- 

 vinced that the fungus was the disease." This, he says, ib 

 going a little too far. Wa have already disposed of "every- 

 body." Everybody does not believe in the rotundity of the 

 earth even in this year of grace. Then as to whether it is in 

 the least degree astounding that a fungus should produce 

 disease, "Amateur" does not say that it is, and may not 

 think so. But why review the several speculations when he is 

 inclined to believe in the fungus, if there is not Eome diffi- 

 culty? He can scarcely fail to find that it has the beet sup- 

 port, and if so it is the first thing to follow np. What wonder 

 need there be ? It is well known that plants are frequently 

 the hosts of other and usually lower forms of vegetable life, 

 very commonly a fungus. Mistletoe grows on the Apple tree ; 

 seeing which with the nuked eye, we bslieve and have no diffi- 

 culty. It might be called an Apple disease. Innumerable 

 instances may be cited of all kinds of paraeitism down to the 

 attack of a roadside weed by a fungus. The case of Mistletoe 

 on the Apple is truly analogous so far that the one is a parasite 

 destroying more or less the other. That the fungus is micro- 

 scopic does not render it a less likely cause. Nature is great 

 in the infinitely little, and much of the highest importance 

 may there be found. We are told of organisms which the 

 strongest microscope is unable to make visible, yet they live 

 «nd have their being: thi3 on the authority of Prof. Tyndal!, 

 to whom "Amateur" refers, about which we shall presently 

 speak. En parentliese we may remark that these organisms 

 are known of course only by scientific deduction. Vegetables 

 growing ou vegntables are common enough, but are less won- 

 derful than the cases of vegetable parasitism on animals, the 

 human race even being liable to the attack of a fungus. 

 " Favus " is a disease caused by the attack of Achorion 

 Schoenleinii, which attacks the part of the human head covered 

 with hair, into which th«. spores grow, producing complete and 

 permanent baldness. Wa have to believe a great deal that 

 does not appear possible at first sight. The skin of a pig— it 

 cannot be well known — will graft on the human flesh. This 

 is rather revolting, but necessity knows no law. It has been 

 used in a case, when the supply of human skin failed, for the 

 purpose of covering a surface on which the natural skin could 

 not grow. It has nothing, whatever, of course to do with 

 Potato disease, but is nsfful to mention while wo have proba- 

 bilities Tinder discussion. A number of different forms and 



species of fungus are known which inhabit the body of the 

 living animal. Instances need scarcely be given. Suffice it 

 to mention Botrytis Bassiana, an ally of Peronospora, which 

 causes the muscardine disease so destructive to silkworms ; 

 Sphseria Robertsii of New Zealand, which grows from the 

 head of the larva of a moth, itself 2 inches long or little more, 

 and the fungus 8 ; and the Cbinese S. sinensis on a caterpillar, 

 having the interest of being used as food. All this being true 

 there is nothing more natural than a fungus affecting the 

 Potato even to destruction. 



" Amateur" steps within the bounds of medical science for 

 illustration and takes the measles, not appearing to be aware 

 that infectious diseases do not always result from infection. 

 Given the necessary conditions and the disease may appear, 

 then forming a centre of contagion. This would be true for 

 measles if we accept the theory of the glandular origin of 

 such diseases, and may be so in any case ; but whether Adam 

 bo suffered or not must always remain an open question. Pro- 

 bably, if he came within the conditions, he did (some one 

 started with that affliction) ; then possibly Eve had them by 

 infection. Eve first ate the forbidden fruit, perhaps she first 

 had the measles in consequence. I fail to see how the "if 

 not" and "why not" would be worth the attention of a 

 medical student. 



" Amateur " nest speaks of Professor Tyndall and sponta- 

 neous generation, but there falls into error. Professor 

 Tyndall's experiments go to prove that the spontaneous gene- 

 ration theory is untenable, not the reverse. " Amateur " does 

 not believe in it, and appears to be right ; but how does he 

 reach his conclusions ? Not, it would seem, by deduotion from 

 the experiments of others or by his own research. Speculation 

 or opinion will not do for this or Potato disease so long as 

 either can be brought under investigation. 



Much of the speculation reviewed must be passed over in a 

 body, not according, as it appears to me, with the light of 

 present knowledge, and therefore my remarks must be limited 

 to that which bears on Peronospora. Degeneracy* (debility), 

 atmospheric influences, &e., may no doubt place the Potato in 

 a position less able to withstand the attacks of its enemy, but, 

 this enemy absent, no amount of " degeneraoy " or anything 

 else will produce its effect. The development of this disease 

 appears to show that the fungus is the cause and not the con- 

 sequent. It has been placed before us by authorities who 

 have investigated carefully, and therefore must be accepted by 

 all who do not probe the matter as fully themselves. With 

 regard to spread, it must be remembered that the fungus has 

 been supplied with the conditions of increase by cultivation of 

 its host, the Potato. This disease and others of a like kind to 

 which economic plants are liable must be taken as the penalty 

 man has to pay for cultivating their subjects in masses, and 

 he must therefore aocept the net result. Plants are widely 

 affected in a state of nature, but then are comparatively 

 isolated. Often are flowering plants introduced to other 

 countries on conditions, whsre th°y attain a development un- 

 known in their original habitat. Very likely it is also the case 

 with certain fuDgi. Possibly the Peronospora grew on another 

 plant altogether, whether in this country or another, but in 

 the Potato found a host more agreeable to its requirements. 

 " Amateur " says very little with regard to origin, and it is in 

 the above sense no doubt he intends the word to be taken. 

 Very little indeed can be said, or rather nothing at all, till it 

 is found truly and certainly wild. 



To trace the fungus through past time is no doubt an im- 

 possibility. We have knowledge, however, thus far, that 

 countless ages ago it miy have existed in much the same form 

 as now. Tne oldest fungus on record has not long since been 

 discovered, and it is a remarkable fact that while similar in 

 other respects its zoospores are the same in form and dimen- 

 sions with those of Peronospora when measured to the ten- 

 thousandth of an inch. This is the fossil Peronosporites 

 antiquarius, found in the vaeoular structure of the axis of 

 Lepidodendron, one of the gigantio Club Mosses of the car- 

 boniferous epoch. 



" Amateur " does not in precise words define his theory, 

 but from his illustrations it appears to be that of an organism 

 coming from somewhere — in any case a parasite. What, then, 



* This word most here be used with a limited meaning. It cannot be 

 admitted with the s*use that a variety of a plan' propagated by extension of 

 an original .individual "rim-* out" by long, cultivation, as has been said of 

 the Bibston Pippin and other frails. Whether they know it or not, p. oplo 

 generally menu a functional disturta-co or weakness, which may result from 

 a variety of causee. 



