GEOGRAPHICAL DISTRIBUTION CLIMATOLOGY. 101 



range, the Serra do Mar. Similarly the enormous evaporation from the 

 north Atlantic is constantly drifted towards the Cordilleras of Venezuela 

 and Colombia by which it is arrested and condensed, the rains on the 

 upper slopes of these iiioimtains being continuous nearly tliroughout 

 the year. 



The distribution of orchid life over the region under review will 

 now be clearly understood. AVithin what is often called the 

 equatorial zone^ a space extending to about twelve degrees on each 

 side of the equator, and which includes nearly the whole of the 

 Malaysian Archipelago and a great part of the continents of Africa 

 and South America the climatic conditions are such that epiphytal 

 and other tropical orchids are generally distributed, even in Africa, of 

 whose tropical vegetation much yet remains to be investigated. It 

 is within this zone that monopodial orchids attain their greatest 

 development ; in Malaysia are found gigantic Stauropses and Gram- 

 matophyllums; in Africa giant Angraecums cling to massive Baobab 

 and Iron- wood trees ; and of sympodial orchids gigantic Eulophias 

 and Lissochili occur in certain places in the Congo and other regions 

 of equatorial Africa in such quantities as to supply a feature in 

 the landscape. Beyond this zone, both on the northern and southern 

 sides, the distribution of orchid life is much more irregular, being 

 immensely influenced by local causes, especially by the direction of 

 the trade and periodical winds by which the evaporation of the ocean 

 is carried into certain localities more than in others, and also by 

 the height and trend of the mountain ranges. 



A few well-known instances need only here be noted. In the eastern 

 section — the mountains of Aracan and ^Nloulmein which receive tlu- 

 south-west monsoon on their western slopes are the richest Dendrobo 

 and Vanda districts known. The Khasia Hills and the lower Himalayan 

 zone upon which, as already stated, is precipitated much of the enormous 

 evaporation raised in the Bay of Bengal is also an exceptionally rich 

 Dendrobium region, and is besides the home of the finest Cadogynes 

 and Cymbidiums yet discovered. In the western section — on tlie 

 Cordilleras of Venezuela and Colombia are aggregated most of the finest 

 Odontoglots, Cattleyas of the lahinta type, Miltonia.s, Lycastes, Mai5de- 

 vallias, and numerous others highly valued by cultivators, caused by 

 the constant action of the north-east trade wind in rendering the 

 climate peculiarly suited to orchid life. And from the action of 

 the south-east trade wind, the coast range of Brazil with the country 

 ni its immediate vicinity is the home of many of the most lieautiful 

 Cattleyas, Lselias, Oncids, Zygopetalunis, Sophroniti's and other orchids 

 prized for their large and brilliant tlowers. 



