86 



the summer temperature rises so high and the winter temperature falls so 

 low that growth, whicli normally should be continued uninterruptedly, ceases 

 for the time being. 



Cocoa, however, to a more marked degree, requires a uniform high 

 amount of moisture in tlie air and soil together with shade and protection 

 from the wind ;- — it can scarcely ever become too warm for cocoa. Where 

 ii is cultivated, i. e. the narrower tropical zone up to an altitude of 500 m., 

 it developes numerous forms but in all ecological varieties, the same re- 

 quirements are felt as to the climate. Fesca (I.e. p. 240) recommends the 

 consideration of its need of shade especially when the plantations are young. 

 Zehntner^ describes a disease affecting these plantations. It appears 

 in the form of brown specks on the bark of two or three year-old sap- 

 plings. After transplantation, the little trunks are more exposed to the 

 wind and the sun and the bark cracks open in different places. 



2. SLOPE OF THE SURFACE OF THE SOH.. 



The slope of the surface becomes a factor which must be considered 

 when the local changes due to the influence of the geographical position are 

 studied. Inclinations (^f from 1° to 10" and at the most 15° are the most im- 

 portant, for greater incUnations are less suitable for fields. Noll- has 

 reported an advantageous result of the inclination of the soil. His ex- 

 periments showed that, on rolling land artificially made, an increase of the 

 cultural surface is obtained which in growing lettuce increases the yield 

 about 31 per cent. But even a slight inclination has disadvantages since 

 rainstorms gradually carry off' the friable earth leaving the sub-soil behind. 



The point of the compass toward which the cultural land slopes is also 

 very important. Southerly or southeastern slopes are most subject to dis- 

 aster because of the great weather changes. The higher temperature pre- 

 vailing here forces the growth rapidly in spring; in summer the danger of 

 drying is greater, for the soil is exposed not only to the south winds but also 

 to the dry east and southeast winds and anyway to the cool, damp west 

 winds, but is protected from the nortli wind. Since, however, dry winds 

 prevail during the spring, i. e. the important vegetative period, the 

 southern declivities dry out very especially and consequently in mountains 

 the southern side is replanted with great difficulty, hence is usually bare. 



The advantages of the southern exposure are most marked in short 

 cool summers. Because of this decli\ity short lived plants will often ma- 

 ture their fruit only in such positions ; hence these slopes are best used 

 for the cultivation of such plants as are grown on account of their fruits 

 and needing the increased action of warmth and light. A colder exposure, 

 however, would be used to better advantage for such plants as are utilized 

 for foliage and wood. 



5 Proefstation voor Cactio te Salatiga. Bull. 4. 



^ Noll, Verg-leichende Kulturversuche. Cit. P.ot. Jahre.sb. 1900. II, p. 304. 



