EFFECT OF SHADE ON COCA. 13 



is even more pointedly of interest, sineo in the mountains of Bolivia 

 the shade system in use for coffee is also applied in the cultivation of 

 coca {Erythroxylon coca), from which the well-known alkaloid cocaine 

 is extracted. As no direct investigations of the qualities of shade- 

 grown and sun-grown coffee seem to have been recorded, the following 

 note by Dr. H. H. Rusby on the effects of shade on coca is worthy 

 of quotation: 



It is here generally believed that shade tends to the production of the best quality 

 of leaves; so the cocales are planted thickly with a small broad-topped leguminous 

 tree related to the St. John's bread, but whose name I can not at this moment recall. 

 There is no doubt that this is a mistake. I have made repeated comparative assays 

 of shade-grown and sun-grown leaves from adjoining plants, and invariably found 

 the latter much richer in total alkaloids. I judge the custom to have arisen from 

 two considerations. There is, as I have stated, a period of two or three months 

 when the plants receive no rain, and then these trees afford a protection from the 

 fierce heat; secondly, shade conduces to the production of a large, smooth, beautiful 

 leaf, of elegant color, and thus adds to the appearance of the product. 



It is further noteworthy that, as in the genus Coffea, the numerous 

 lowland species of Erythroxylon are greatly inferior to E. coca in 

 cocaine content, suggesting that in nature as in the shaded plantations 

 examined by Dr. Rusby the alkaloids stand in a direct relation to the 

 powerful insolation permitted by the transparent mountain atmosphere. 

 But as the shade-grown coca leaves, although deficient in cocaine, 

 appear to be acceptable to the coca-chewing Indians, it may be that 

 other desirable qualities are not eliminated by shade growth, 1 though 

 this seems improbable in view of the fact that the products of high 

 altitudes are, as in the case of the coffee, considered superior, not 

 merely on the account of the presence of more cocaine but of other 

 substances grouped as " sweet alkaloids" which impart to the finest 

 leaves their characteristic aromatic flavor. Dr. Rusby even supplies 

 us with a physiological theory to account for the relations between 

 quality and altitude. 



I have made a large number of assays tending towards elevations, soils, exposures, 

 seasons, ages of plants and of leaves, different varieties, wild and domestic, different 

 parts of the plant, and various modes of drying and packing. The results will be 

 embodied in a future monograph, mere passing reference being made to them for 

 the present. I have about concluded that the percentage of the sweet alkaloids 

 varies inversely as the amount and continuousness of moisture that the plant receives. 

 Thus, the Peruvian, Ecuadorian, and the Brazilian coca, which, as I have stated, is 

 much more copiously and regularly watered than the Bolivian, is markedly inferior, 

 so that Bolivia regularly exports about one-eighth of her crop to those countries. I 

 am inclined to think that the greater breadth and thinness of the northern leaf may 

 be partly due to the greater water supply and the consequent greater degree of evapor- 

 ation. Again, the Indian always seeks the coca grown at the higher elevations, 

 where the humidity is much less and more irregular than in the districts along the 



a The failure to complete the changes necessary in forming the alkaloids might also 

 leave undesirable substances in leaves or fruits grown in the shade. 



