Manuring.—The application of manures is unattended by any apparent increased growth of the trees ; but, except in the case of red barks, is aocompauied by a marked increment in the proportion of alkaloids contained in the bark. Dung applied to crown hark, 3-4 times in 5 years, iuoreased the alkaloids 2•81 per cent., thus raising the value of the bark by about 2s. 6d. a lb. ; 1 lb. of guano per tree, gave 2.5 per cent. increase (1s. 6d. a lb ); lb. sulphate ammonia gave 1.22 per cent. increase.
Diseases.—Two distinct forme of disease are said to attack the plants: the one, constitutional, affecting the whole plant, and generally fatal ; the other, local, and not dangerous. The former is almost identical with the "canker" of English gardeners, and is induced solely by inefficient drainage ; it is first manifested by the discoloration and falling of the leaves, followed by shrivelling of the tissues from the roots upwards, and quickly terminating in the death of the plant ; it is neither infectious nor contagious, but purely local, and due only to excess of moisture in the soil. The second form of sickness appears in patches on the stem and branches, quite local in character ; very rarely it involves the whole stem, when death may result, but frequently the diseased spots are thrown off, and replaced by new healthy bark, and when much affected trees are out down, the stumps throw up vigorous shoots ; its cause is not yet well explained.
Harvesting the Bark.—In S. America, barks of all sorts and ages are collected indiscriminately, and in such a way as to kill the trees; snob a system was evidently inadmissible in the case of cultivators, and the several improved plans proposed will now be described. The first of these is known as "mussing," and is illustrated iu Fig. 580. Two parallel cuts c are drawn down the 3 F 2 stem, the strip of bark a included between them is then raised from the incisions, and pulled off carefully from the bottom upwards, great care being taken not to injure the cambium, or sappy matter, left in the hollow; immediately the bark is removed, a thick coating of moss b is bound around the wounded stem. By this process, the cambium granulates, and forms a new bark. It is essential to observe that the moss is free from lichens. The strips of bark removed are about 1-li in. wide ; such a number are taken as the tree will afford, leaving intermediate strips of somewhat greater width. At the end of 6-12 months, the bands left in the first instance are taken in the same way ; in 12-22 months, the parts first stripped will be covered with new bark ready for re-stripping. The advantages claimed for this plan are that a crop of bark equal to half the total trunk-bark of the tree can be taken annually, without damage to the tree ; and that this bark is richer in total alkaloids, and especially in crystallizable quinine, than natural bark. It appears, however, that this increase of total alkaloids is not observable in the renewed bark of trees at the maximum yield (over 8 years) ; but the proportion of quinine is augmented, and the value of the bark as a source of pure quinine is thereby raised. The enrichment of the renewed bark is said to be at the expense of the bark outside the mossed region ; and it is said that the renewal is prevented, or much retarded, by the least injury to the cambium. Further, the cropping cannot be
depended upon oftener than once in 2-3 years ; and this rapid cropping tends to shorten the lives of the trees. Finally, the operation can only be performed when the air is quite moist, and therefore at a time when the bark can least easily be dried.
In some instances, too, the plan has been frustrated by the renewing bark being devoured by ants, who found an asylum in the moss. On the other hand, a number of trees which were left bare (unmossed) after the barking, renewed their bark fairly.
well. When sufficient supplies of moss cannot be procured, as for instance in Coorg, substitute is found in detached leaf stalks of the plantain, and the leaves of wild cardamom, or of ginger. These should be applied in a dry state, and not with a smearing of clay, as has sometimes been done.
An alternative to the mossing system is that described as " coppicing." The trees are cut down near the ground, and of the shoots which spring up from the stump, or "stool," as it is termed, one or more are left to grow. The alkaloidal richness of the bark is supposed to attain its maximum at the eighth year, which period might be chosen for the coppicing, and a regular succession of shoots be cut as required. As yet, this plan has not received the same study or encouragement as the preceding, and against it are alleged the following objections :—That the stool frequently fails to send up shoots ; that the rate of growth is slower than in young trees ; and above all that for every 6 lb. of trunk-bark per tree by the mossing system, only 11 lb. of mixed trunk and branch bark were obtained by coppicing, but these 6 lb. included 3 lb. of original bark. It is probable, as King suggests, that a compromise between the two systems will ultimately be adopted, mossing for a time and coppicing when the vitality of the trees begins to be impaired. As a matter of fact, much remains still to be learnt as to the natural longevity of the trees, the effects of shade at all ages, the respective value of the bark from different portions of the tree, and other points of great importance, which can be elucidated only by intelligent experiments conducted on a large scale.
Removing and Drying the Bark.—At some seasons, the separation of the bark from the wood is very easily effected, and these should be chosen for the operation. Felled trunks and branches are scored with a number of longitudinal and transverse incisions, which liberates the bark; smaller branches and twigs are subjected to whittling, and as much of wood as possible is excluded. As soon as removed, the bark is spread to dry on split bamboo shelves in rough temporary sheds ; the process can be completed only with artificial heat, for which purpose the partially dry bark is con veyed to the drying-house, a stone building, erected near the alkaloid manufactory, provided with shelves, and heated to temperature exceeding that of the outer air by about 10°-15° F. The heat must never rise so high as to affect the chemical composition of the bark. After proper drying, the bark can be stored without suffering deterioration.