DENDBOBIUM. » 



Approaching the equator the climatal phenomena become more equable. 

 Within the equatorial zone, or that portion of the earth's surface that 

 extends to about 12 degrees on each side of the equator, a space that 

 includes the whole of the Malay region, the most characteristic feature 

 of the climate is the wonderful uniformity of its temperature alike 

 throughout the changes of day and night, and from one part of the year 

 to another. As a general rule the greatest heat of the day does not 

 exceed 32°— 33° C. (90°— 92° F.), while it seldom falls during the night 

 below 23° C. (74° F.). It has been found by hourly observations carried 

 on for three years at the meteorological observatory at Batavia, that the 

 extreme range of temperature in that period was only 15° C. (27° F.), 

 the maximum being 35° C. (95° F.), and the minimum 20° C. (G8° F ). 

 The usual daily range of the thermometer is, on the average, only a little 

 more than 5° C (about 10° F.).* During a large part of the year, the 

 air of the equatorial zone is nearly saturated with vapour, and, owing 

 to the great weight of vapour, its high temperature enables it to hold in 

 suspension, a very slight fall in the thermometer is accompanied by 

 the condensation of a large absolute quantity of atmospheric vapour, so 

 that copious dews and heavy showers of rain are produced at compara- 

 tively high temperatures and low altitudes. The yearly rainfall at 

 Batavia is 78 inches. During the wet months of the year, it is rare to 

 have many days in succession without some hours of sunshine, while 

 even in the driest months there are occasional showers, f 



Although northern Australia is situated within the tropical region, 

 the rainfall is there more restricted, and the amount diminishes in 

 proceeding southwards ; in many places even near the east coast, where 

 the precipitation is greatest, it scarcely exceeds the average annual fall 

 in many parts of England ; but on the eastern slopes of the coast 

 ranges of Queensland, the rainfall is more copious, and there accordingly 

 the Australian epiphytal orchids attain their greatest development. 



The greater part of the Philippine Islands being within the equatorial 

 belt, they are subject to nearly the same climatic phenomena as the 

 islands of the Malay Archipelago. Ceylon, however, although situate 

 within the equatorial zone, possesses two distinct climatic regions : the 

 smaller south-western portion, which is separated from the larger north- 

 eastern portion by the mountain system of which Adam's Seat is one 

 of the highest summits, has a climate that agrees in the main with 

 that of the equatorial belt; whilst the larger north-eastern portion is 

 subject to long droughts, and has a greatly diminished annual rainfall ; 

 in this portion orchids are almost entirely absent. 



Cultural Notes. — The facts stated above relative to the climate of 



the region in which the Dendrobes have their home, supply data for 



the guidance of the cultivator, but not the rule to be followed. They 



simply teach him that as regards temperature there is a lower limit 



* Wallace's Tropical Nature, p. 4. t Idem. pp. 15 — 18. 



