CHAPTER V 



TROPICAL DISTRICTS WITH PRONOUNCED 

 DRY SEASONS 



I. General Characteristics of the Vegetation in Periodically Dry Tropical 

 Districts. Fornialions. Xerophilous trees. Xerophilous shrubs. Lianes. Epiphytes. 

 2. Woodland Formations in Periodically Dry Tropical Districts. i. General 

 :Uniayks. Transformation in woodland vegetation by gradual transition from constantly 

 humid to periodically dry districts. Chief types of woodland : monsoon-forest, savannah- 

 forest, thorn-forest, ii. 'I'ropflphilous and Xerophilous Woodland in India. Forest 

 vegetation in Pegu according to Kurz. Forests of Tectona grandis in East Java, 

 iii. Woodland in Tropical East Africa. Engler's description of the formations, iv. 

 Tropcplnlous and Xerophilous Woodland in T?-opical America. Savannah-forest in 

 \'enezuela. Thorn-bushland (caatinga) of Brazil. Thorn-bushland on the limestone 

 hills in Minas Geraes. 3. Tropical Grassland Fcrmations. i. General Character of 

 >r.annah. ii. Savannah in Africa. Savannah on the Loango coast according to 

 i tchuel-Losche. The baobab. East African savannah according to H. JNIeyer and 

 I'ligler. iii. Sax'annah in America. The llanos. The campos of Brazil according to 

 \\'arming. 



I. GENERAL CHARACTERISTICS OF THE VEGETATION IN 

 PERIODICALLY DRY TROPICAL DISTRICTS. 



Trotical districts with either one or two pronounced dry seasons, 

 several months long, particularly occupy the interior of continents, and 

 include nnuch greater areas than do those with a constantly humid climate. 

 Their v^egetation never attains the luxuriance of the rain-forest, and above 

 all bears the impress of a less favourable environment. The dry periods 

 bring the vegetation of the tropics oecologically nearer to that of the zones 

 that are cold in winter, because physiological dryness of soil is caused b}' 

 a scarcity of atmospheric precipitations, as well as by cold. 



Whilst the constantly humid districts are uniformly clad with evergreen 

 rain-forest, the periodically dry districts present a much more varied 

 appearance as regards vegetation, inasmuch as slight differences in the 

 climate cause a rapid change in the t}pe of formation, and edaphic 

 influences are much more effective than where the soil is always moist. 



Districts with very abundant rainfall during the wet season, if they have 

 pronounced dry seasons accompanied by great heat, are clad with luxuriant 

 forests the trees of which lose their hygrophilous foliage during the dry 



