December i, 1882.] 



THE TROPICAL AGRICULTURIST. 



489 



such numbers as to cause the impression that the trees 

 are deo^iying fast ; the unnatural excess of fall is called 

 leaf-dieeaae, although little fungus can be seen. The 

 ruling condition where leaf-disease prevails ia a parched 

 or repressed condition of the roots, and oftentimes of 

 the lower roots only, which even in showery weather, 

 towards the close, or iifter the monsoon, will be often 

 found to underlie a deceiving cover of wetted soil, whicli 

 supplies the leaves and top roots only with the lacking 

 moisture. It is only heavy, continued, or repeated 

 showers, which get througli a stilf or hardened soil 

 down to the netlier roots. In these times of the year, 

 both upper and lower roots are liable to dryness, 

 and, in ratio to the nature of the subsoil, the proteo 

 tion or not, by mould and the foliage of the tree 

 even a salutary influence must be effected by moist- 

 ure given off by adjacent forest. To tlie severe 

 effects of these recurring seasons in dry districts, 

 upon coffee in thin and worn-out soil, is due much 

 of the abandonment which took place before disease 

 was known. During dry weather, as is known, new 

 land and free or tilled soil afford immediate access 

 to the roots to rain and dew and with little waste. 



On the fine old estates which still keep to the front, it 

 is not to be expected that the trees generally can 

 now bear as they did — they are aged, and their 

 circumstances of growth are much reduced. The 

 forest forming these estates was carefully and fortun- 

 ately selected. For many years the soil continued 

 free, deep, and rich. The multitudinously grown 

 rootlets felt no restraint below, nor repression above 

 from loss of mould and the thinning shade of a 

 tailing tree. Subdrainage was well effected in the 

 free and unconsolidated earth through chink and 

 channel left by root and worm. Reservation of moist- 

 ure was sufficiently preserved by the mould and the 

 free soil, assisted by decaying roots and timber. 

 Food was everywhere and was for years supple- 

 mented by the mouldering remains of heavy forest. 

 In higialy cultivated gardens alone could such pro- 

 pitious conhtions for growth be artificially effected 

 and trees there would be twice or thrice renewed 

 within the time tliose patriarchal trees have stood. 



The remedies for the repression of coffee leaf-dis- 

 ease and against infertility will in lime prove useful 

 to other products. The remedies can happily be 

 applied as one ; and it is : attention to the roots, 

 encourage and sustain the growtli and the renewal 

 of the rootlets, by keeping the soil free, by supply 

 of food, and the regulation of moisture. 



Experiments and observations on a few trees or 

 on a tield will test these assertions and they are 

 not new from me. R. 



WHAT AILS OUR COFFEE TREES ? ANSWER : 

 LEAF-DISEASE. 



.30th October 1882. 



Dear Sir,— "W.," in his second letter, tells us 

 that the sole object of his first was to prove that 

 hemikia was not the primary cause of the universal 

 decline of the fruit-beiiring powers of our coffee tri-es ; 

 his demonstration really taking the form of the 

 enthymernc : — (1) Cofi'ee was cultivated for years with- 

 out attracting the disease; (2) an unhealthy consti- 

 tutional condition is a sine qua non for the establish- 

 ing of a fungoid growth in any organism ; (3) leaf-disease 

 did establish itself in our coffee ; therefore, our cffee 

 was in an unhealthy state prior to the attack of hemileia. 



This logical conclusion must, bowever, be condemned 

 as blind, empirical, and h.iphazard. being directly 

 opposed to that arrived at by Marshall Ward after 

 long and careful study. He proved beyond a 'loubt 

 tiiat " a spore, taken from a diseased leaf and sown 

 on the lower surface of a healthy coffee leaf in a drop 

 of water, germinates." 



Let us pretend to ignore for a moment this judg- 

 ment of the cryptogamist, and see how far " W." 

 has made out his case on his own hypothesis. Ac- 

 cepting this, if we critically analyse the word 

 "primary," giving to it its two senses of priority 

 of time and place, there will hardly be any of us 

 so bold as to deny that on the lirst count "W." 

 has proved his case. But, sir, where shall we stop 

 if we attempt to unravel the mystery of the first 

 cause of leaf-disease's existence ! Surely " W." is 

 arguing on false premises when he tells us (letter 

 No. 7) that it is ridiculous to suppose the leaves 

 and permanent structures of our trees have any inter- 

 dependence. 



The leaf we all know to he one of the conserv- 

 ative organs of a tree, and (if a temporary one) ia 

 as absolutely necessary to the growth and preserv- 

 ation thereof while it remains on it, as lunge to 

 an animal. It seems to me as unreasonable to sup- 

 pose that a diseased leaf will elaborate naturally 

 pure juices for tlie system of its parent tree, as 

 that humanity can touch pitch with impunity or 

 that jelly filtered through a bag saturated with 

 kerosine oil will turn out a palatable condiment. 



In previ.jus letters I have ventilated my belief in 

 an existing analogy between the two kingdoms, 

 animal and vegetable. This I maintain in the face 

 of "W."'a dogmatic assertion that the theory of a 

 vegetabl'1 circulation is absurd. It would, therefore, 

 be the basest apostacy on my part were I to allow 

 his inference (that the leaf is not as necessary to 

 the tree, as any member or membrane to the human 

 entity) to pass unnoticed. Though a cabbage may 

 not be able to apply the moral, the sense of the 

 fable of the "belly and the members " bears equally 

 on its constitution and a king's. Still harping on 

 this analogy, let me adduce a case which seems to 

 me to parallel poor coffee's present state. Last crop 

 a cooly (male), in the prime of life, met with an 

 accident which necessitated the amputation of a leg. him 

 Shortly after his return from hospital, his wife left 

 for a younger, whole man. * ♦ • Leaf-disease has 

 amputated poor coffee's leg, and he can do next to 

 nothing in the way of reproduction, and may be ex- 

 pected before very long to hobble off the "hooks." 



The 3rd para of the 7th letter savours strongly of 

 suppressio veri. Though the disease does not enter 

 through its roots, as " W." there declared, he omitted 

 to add that it is quite possible tliat the whole tree may 

 be affected by a vitiated elaboration of the sap in the 

 leaves. I do not hold with " W." 'a fears that, even if 

 we expelled the disease, it would be bound to return, 

 nor do I think for a moment that our coffee would still 

 remain uuproductive if such a crusade were success- 

 fully carried out. It is interesting at this stage to 

 recall Dr. Trimen's ideas ccmveyed in his covering 

 letter to Marshall W^ard's 3rd report. " We know," 

 he wrote, " that there is one sufficient cause of leaf- 

 disease, the uredospore of H. V., that is produced only 

 by a pi evious one, and can germinate only in moisture. 

 This then is a vei-a causa, and in accordance with the 

 wellkiiown medical aphorism, to remove this would 

 be the true practice." There is no pursuit of phantoms 

 or first causes suggested here, but a measure which only 

 our increasing poverty renders daily more and more 

 impriuticable to us, the entire destruction of the 

 accursed spores. Why cannot " W." accept this doct- 

 rine with ttiat faith he exhibits as to the unexplained ex- 

 istence of the first canse of all these minor first causes 1 

 In his first letter " W," by way of pointing out 

 the harmlessness of leaf-disease, tells us of a group of 

 estates that gave satisfactory crops in 1S76 although 

 just before the hlossomiuL, time these estates were 

 nearly leafless. It is a moot point in luy-mind whether 

 leaves are of such importance to the tree at the peri, id 

 of blossoming — when the tree's energies go to the 



