434 



THE TROPICAL AGRICULTURIST. 



[November i, 1882. 



THE "FATAL PUNGTJS " AND IND EFFECTS 

 ON THE COFFEE TREE. 



"W.'s" letter given below, will, like all his 

 writings on coffee culture, be read with respectful 

 attention. But in denouncing the popular belief in the 

 fatal effects of the fungus, as unscientific, we suspect 

 "W." himself will stand alone amougst scientific men. 

 We are not aware that the quack who propounded the 

 "internal iilcer" theoiy had a single believer in his 

 absurd theory. We all know and believe that the 

 evil is in the leaf. The fungus enters it by its stomata 

 and feeds on the contents of the cells, the very life- 

 blood of the plant, and crop after crop of leaves pro- 

 duced by the plant for its ovra sustenance, used for 

 the sustenance of the parasite and then dropped, have 

 a very different effect on the strength of the plant 

 to leaves withering and dropping after they had per- 

 formed then- nourishing function. Under continuous 

 attacks of the fungus and repeated attempts to renew 

 foliage necessary to its own existence, which only 

 go to feed its foe, the tree becomes so debilit- 

 ated, that it cannot mature its fruit. Mr. Hughes 

 has shewn, what no one knows better than "W.,"tliat 

 a tree can be exhausted by too frequent production 

 of leaves, as well as by over- bearing of fruit crop. 

 Wind is a terrible evil in depriving the coffee tree 

 of its leaves and were tearing winds to become as 

 permanent in existence and operation as heniileia the 

 effect on the coffee bushes would be much the same. 

 But bad as " wind, wash and weeds," the planters' 

 thi'ee great enemies are, the three combined, do less 

 mischief than the ever present and almost ever active 

 fungus. 



With all respect to "W.," we feel it right to say 

 that we adhere to our opinion. It is tliat while 

 coffee has suffered much from abnormal seasons in 

 the past decade of years, and from other causes, — 

 notably insect pests, — its great enemy has been, and 

 continues to be hemileia ra«falri.r. Even when torn 

 off by winds, leaves gave back fertilizing mineral 

 matter to the soil. In tlie case of leaves destroyed 

 by the fungus, tlie fertilizing matter has gone to feed 

 the parasite and increase its power for mischief. Other 

 causes, many and potent have worked against the 

 coffee tree and those dependent on it. But the sudden 

 development of a new fungus, peculiar to coffee in 

 1869, its rapid spread and its "fatal" effects, have 

 done more harm to the coffee enterprize than all other 

 causes combined. If the vu-ulence of this one pest abated, 

 we should soon cease to ask the question " What ails 

 our coffee ?" 



WHAT AILS OUR COFFEE TREES? No. 6. 



SiK, — Hemileia has evidently become far too con- 

 venient a scapegoat, and has been too long accepted 

 to be easily relinquished by many who have accustomed 

 themselves to imagine it an adequate cauee of the 

 recent infertility of our coffee trees, notwithstand- 

 ing that the theory ia equally opposed to logic and 

 to facts. 



The only correspondents who defend the fatal fungus 

 theory with any show of reason assume that the pest 

 was carrying on its destructive work insidiously and 

 uuifcrsally on our estates prior to 1871, although it 

 was unobserved except on a very few. Before the 

 true nature of the Hemileia and its attack vviis fulij 

 ascertained, .some high authorities believed the pest 

 to exist uneeeu in the inti'rnal tissues of the tre'S, ard 

 to develop itself thi-re unol'servcd. But this hy|uithesis 

 was always doubLful, aud was eventually demolished 

 by Mr. Ward's complete- exposition of the life 'nistory 

 of iihe fungus, and the precise method of itS' attacks. 



The external origin of the disease was thus fully estab- 

 lished, and it was proved conclusively that the leaf 

 was the sole seat of the attack, and that the operation 

 of the disease is therefore manifest. The assumption 

 that Hemileiet might have been insidiously c.irrying on 

 unseen mischief ia therefore entiri-ly erroneous, and the 

 only argument by which the universal failure of crop in 

 1871 could be attributed to leaf-disease falls to the 

 ground. In fact, as has already been shown in pre- 

 vious letters, the theory of the fungus being the 

 potential cause of the short crops of the past decade 

 IS logically untenable, inasmuch as the alleged effect 

 preceded the cause. And it is also opposed to fact, 

 as there has been throughout the decade the greatest 

 discrepancy both in point of time and intensity be- 

 tween the so-called cause and its operation. 



Setting aside, however, both the logical impossibility 

 of the theory and the utter want of sympathy be- 

 tween cause aad effect, as thereby implied, it may 

 be instructive to consider the subject from an. 

 other point of view. Seeing the almost universal 

 prevalence of fungal attacks on vegetation, and 

 that coffee is by no means exceptional in . 

 having its fungal parasite, it is well worth con- 

 sidering whether, and to what extent-, Hemileia and 

 its effects on our coffee leaves differ from other 

 parasitic fungi and their ravages on the vegetation 

 around us. If we stroll through the jungle, or 

 along any path in the country, innumerable forms 

 of fungi will meet our view, both on the fallen leaves 

 which are shewn on the ground, and on many 

 leaves still living and clinging to the trees and pLants. 

 Few plants, indeed, will be found to be exempt 

 from the ravages of fungi in some form or other. 

 Parasitic fungi are no strange phenomena, but are 

 almost as universal as vegetation itself. Yet we hear 

 no jeremi.ads on the havoc so committed all around us. 

 No doom is pronounced against the jack, and many 

 other of our most useful trees, which, nevertheless, suf- 

 fer as much as our coffee trees, or more, froni precisely 

 similar kinds of attack ! A few weeks ago, on pointing 

 out to a fellow-pl'inter who was with me a fearful dose 

 of fungus on the leaves of one of our new and most 

 hopeful products, and asking him how it happened 

 tiiat no scare had been got up about this invadci-, he 

 merely remarked that it seamed " so natiirnl^ " he had 

 not regarded it as 3,peH\ lnis^ct,\tvia,& quite natural 

 and the leaves in question were only going the way , 

 of most leaves. The alarm about our Hemileia was 

 inspired by the belief that, like the pot.atoe pereno- 

 spora, it existed in the internal tissues of the tree, 

 aud infected its whcde economy. All serious fears 

 oucht, therefore, to have subsided when tlie true nature 

 of 'the fungus and the method of its attack were fully 

 ascertained. Before this discovery, however, it had 

 been generally accepted as (he cause of all our mis- 

 fortunes, and was not so easily dismissed from the pre- 

 eminence it had attained. Many will etill cling to the 

 fatal fungus theory, and probably regard me as _ a 

 personal enemy for trying to depiive' tliem of it. 

 The history' of a leaf is like that of all vital organ- 

 isms in h.iving a period of growth, or cycle of life- 

 changes, durng which it fulfils its appointed functions 

 for the plant to which it belongs, until it attains its 

 full maturity, when these life changes and these func- 

 tions cease. " The leaf is then no longer an active 

 member of the society in which those life obliges aud 

 functions were fulfilled, but passes through death into 

 a passive state, and liecomes subject to a new cycle 

 of changes, in the course of which its substance is 

 either reconiposed or dissipated. The passive remains 

 of ihn once active or^auism may still cling to the pluce 

 of its birth and activity, but its work is done ! It ia 

 but a crpse, and the undertaker, if he have not 

 already with indecent haste anticipated the event, 

 is'et'cr ready to begin liia work. The dclunct 



