DISEASES INDUCED BY SHADE. 29 



time to become reestablished and exert an appreciable effect. The 

 fertility, however, is not sustained, and generally decreases measurably 

 after the first season, probably more because the soluble materials are 

 washed rapidly away than because of exhaustion by the year's crops. 

 How much virtue may lie in the baking of the earth, and how far such 

 a fact could be utilized with coffee or other cultures remains to be 

 determined, but in opening new plantations in mountainous regions 

 the desirability of clearing the lower slopes first is worthy of consid- 

 eration, since to the fertility derivable from the drainage of forest 

 areas would be added that from the tracts subsequently cleared and 

 burned. 



SHADE AND FUNGOUS DISEASES. 



While by no means confined to shaded plantations, it is now admit- 

 ted that the leaf-rust of coffee, due to a parasitic fungus (Hemileia vas- 

 tatrix), is especially virulent on shaded trees, and it has even been 

 claimed that the comparative immunity of Liberian coffee is due to the 

 fact that it has been grown without shade. Investigation of the dis- 

 ease has also shown that the spores germinate only in water, and that 

 they are killed by exposure to sunshine. The desirability of more open 

 planting in situations affording a good circulation of air has been real- 

 ized in Java, and this is also in accordance with the general proposi- 

 tion that vigorous, healthy vegetation is less liable to parasitic and 

 other diseases than that improperly nourished or otherwise debilitated. 

 It happens, however, that, with reference to the present disease, what 

 might appear to be exactly the contrary method has also been found 

 of use. In the Coorg coffee district, on the west side of the peninsula 

 of southern India, it has been sought to avoid the ravages of the Hemi- 

 leia by planting the coffee in forests which have been thinned by the 

 removal of the trees supposed to exert a harmful competition with the 

 coffee. A leguminous species, Dalbergia latifolia, is the favorite of 

 those retained, though two species of Artocarpus and several others, 

 leguminous and nonleguminous, are also considered desirable. The 

 coffee is thus grown under permanent shade from the first, but the the- 

 ory of protection from the disease is quite different from that followed 

 in Java. The forest is intended to serve as a wind-break, which pre- 

 vents the spores of the fungus being carried to the coffee by currents 

 of air, and thus hinders the distribution of the fungus. A recent let- 

 ter from Mr. Oliver Moll, of Ubero, Oaxaca, Mexico, states that coffee is 

 also planted in that vicinity in natural forest, which has been "thinned 

 out sufficiently to permit enough sun on the young plants." The 

 experiment of planting rubber alternately with the coffee is also being 

 tried, and the forest conditions may be chosen on that account, though 

 the results of the arrangement are not yet apparent. 



In Venezuela and Colombia heavily shaded plantations, or those 



