There is, however, no danger of the actual extirpation of the trees unless the plan is adopted of leaving them standing, and stripped of their bark, as in the Loxa forests. Poeppig says that, in these cases, the trees in the tropical forests are attacked by rot with extraordinary rapidity; hosts of insects penetrate the stem to complete the work of destruction, and the healthy root becomes infected. Thus the valuable species called _C. Uritusinga_ has really been almost exterminated. But where the trees are felled it is only necessary to observe the precaution of hewing the stem as near as possible to the root, in order to be sure of its after-growth.[90] Under these circumstances, after six years the young trees are ready to be felled again in the milder regions, and after twenty years in cold and exposed localities. From the base of the stems, when not barked, a number of shoots spring out between bark and wood; and Dr. Karsten says that, though an interval of rest of twelve or fifteen years must be given to the forests where the chinchona-trees have thus been felled, this only promotes further investigation in the endless untrodden forests, while, in the mean time, the younger generation is growing up in those which have already been exhausted.[91] The danger, therefore, is not in the actual annihilation of the chinchona-trees in South America, but lest, with the increasing demand, there should be long intervals of time during which the supply would cease, owing to the forests being exhausted, and requiring periods of rest. In many districts this is already the case. The bark which comes from Loxa is in the minutest quills, and in the forests of Caravaya, after an interval of rest of several years, the root-shoots had scarcely grown to a sufficient size to yield anything but quill bark. Then again the supplies of bark from South America are not nearly sufficient to meet the demand, and the price is kept so high as to place this inestimable remedy beyond the means of millions of natives of fever-visited regions. For these reasons the incalculable importance of introducing the chinchona-plant into other countries adapted for its growth, and thus escaping from entire dependence on the South American forests, has long occupied the attention of scientific men in Europe. In 1839 Dr. Royle, in his 'Illustrations of Himalayan Botany,'[92] recommended the introduction of the chinchona-plants into India, pointing out the Neilgherry and Silhet hills as suitable sites for the experiment, and Lord William Bentinck took some interest in the project. M. Fée had previously recommended the introduction of these plants into the French colonies;[93] and in 1849 both Dr. Weddell[94] and M. Delondre[95] strongly urged the adoption of this measure. The former declared that posterity would bless those who should carry this idea into execution.[96]