174 AGRICULTURAL REPORT. 



tissue which keeps its primitive form, and after some time all the in- 

 terior of the generative zone (cambium) becomes organized into a new 

 woody layer, which adheres to and forms part of the previously formed 

 Avood. ^Vt the same time, in that portion of the generative layer which 

 is in contact with the bark, a certain number of cells undergo similar 

 transformations, assimilating them to, and preparing them to form, a 

 new portion of bark." 



Source of the all-aloids in the rcneiced hayl\ — Mr. Howard prosecuted 

 an extended series of experiments to ascertain the source of the 

 alkaloids formed in the bark. In summing up he says : " We have 

 thus far traced the deposits of the ascending sap in its course from 

 the roots, through the wood, to the leaves, and we do not find any 

 reason to look upon either the wood of the roots, or of the stem, or of 

 the more succulent and recently-formed portions of the ligneous struc- 

 ture as the seat of the formation of the alkaloids. In all these parts 

 the proportion of alkaloid is insignificant when compared with that of 

 the bark. In the outside portion of the stern-wood we find rather less 

 alkaloid and rather more kiuoric acid than in the center-wood, and 

 there is a smaller amount of resin, but a perhaps greater proportion of 

 wax associated with the alkaloids ; they exist in both in a somewhat 

 gTeater degree of purity than in the root. When we come to the leaves 

 we find almost the same proportion of alkaloid as in the wood, but this 

 amount not increased, as would surelj^ be the case if the leaves were 

 the seat of its formation. In tracing the course of the nourishing or 

 descending sap we find the alkaloids increasing fjreaili/, not less than 

 ten or twenty fold, often much more in their relative amount in the 

 liber, as compared with the parts we have passed under review; and 

 what is also very important, they arc in a state of much greater i^urity, 

 as if freshly formed. In the cellular envelope there is again a consid- 

 erable increase, to the extent of 100 or 150 per cent, on the contents of 

 the liber, and the alkaloids, or at least quinine and cinchonidme appear 

 to be especially stored up in this cellular envelope, but this in connec- 

 tion with various substances difficult to separate from them. In the 

 mossed harlcs the alkaloids seem to exist in the cellular envelope in a 

 state of greater purity. The review of the whole seems to point to the 

 darJ: as the seat of the formation of the alkaloids." 



Modus operandi. — The mode of operation by which the alkaloids are 

 developed in the bark was made the subject of many experiments and 

 of very close observation by Mr. Howard, but it is acknowledged to 

 be one of those vital actions which neither the microscope nor the 

 laboratory has yet been able to expose. There seems to be some unex- 

 plained relation between the laticiferous ducts of the liber and the 

 development of the alkaloids, a large development of these ducts being 

 always associated with a poverty of the alkaloids ; and, in proportion 

 as the alkaloids become more abundantly developed, the laticiferous 

 ducts disappear or become much restricted in their size and relative 

 importance. 



Conclusions. — The following arc some of the conclusions to which, jn 

 summing up his experiinents, Mr. Howard arrives : 



First. The permanence of the characteristics of species, as far as 

 ascertained by the present investigation. After all the changes and 

 the varied treatment of the cinchona succirubra, it appears to reraaiu 

 exactly the same in all material points as in South America. 



Second. The cultivation of the chiuchona in India promises complete 

 success, but to insure this, great attention must be paid to the choice 

 of species. 



