Pancratium, a spider lily, has cracked the bare earth in 

 sending up its flower stalk. 



A problem that these plants encounter, both in the tem- 

 f)erate and seasonally-dry tropic zones, is timing. A warm 

 period in midwinter does not cause apple trees to blossom, 

 nor does Haemanthus burst into flower after an unusually 

 heavy rain in the middle of the dry season. Obviously, 

 these plants have internal mechanisms that usually prevent 

 premature flowering. These internal mechanisms, called 

 dormancy requirements, have been extensively stvidied for 

 temperate plants such as the tulip, but they have scarcely 

 been investigated in tropical plants that pass through a long, 

 dry season. I collected a terrestrial orchid in an acacia 

 thorn-scrub vegetation that was flowering in April at the 

 beginning of the rains. This is a very dry habitat for or- 

 chids, and only one orchid species is known from this par- 

 ticular area. This plant was taken to a greenhouse at much 

 higher elevation where the temperatures were cooler and 

 quite consistent throughout the year. It was watered regu- 

 larly, and in the two following years produced inflorescences 



The Crinum plant. Only the leaves and flower 

 stalks are seen above ground. The large bulb stores 

 jood underground during the long dry season. 



only in .April-May. The only reasonable explanation for 

 this precise flowering behaviour is to assume that the plant 

 was sensitive to changes in day length: that the lengthening 

 days of April triggered flower production. But since this 

 plant was living about ten degrees north of the equator it 

 had to respond to a change in day-length of less than 40 

 minutes. In this region the longest and shortest days differ 

 by only that amount. There are probably many other 

 ways in which plants of seasonally-dry areas are stimulated 

 to resume growth at the proper time. 



While the trees and flowering herbs in the seasonally dry 

 tropics give the advent of the rainy season a spring-like 

 aspect, animals also behave as if it was spring. Many birds 

 court and begin to nest at this time. Reptiles that have 

 withdrawn into deep crevices for a period of inactivity 

 during the dry season begin to move about again. This 

 is the time of year when the roadways take their great- 

 est toll, when snakes rarely encoimtered in the bush are 

 found the victims of a passing car. Frogs and even fish 

 that have survived under a hardened roof of mud becoine 

 active once more as ponds refill and rivers start to run. In- 

 sects hatch from eggs or chrysalids, and a new cycle of activ- 

 ity begins. Where only the dry wind could be heard before, 

 there is now a cacophony of sounds; singing birds, buzzing 

 insects and at night the frogs and toads join in. 



For men too, the beginning of the monsoon is a spring- 

 time. In areas with sufficient rainfall the farmer tills and 

 plants his fields. In more arid areas the pastoralist, after 

 many lean months, finds abundant food for his livestock; 

 this is the time for calving and milk is in abundance. For 

 many people the dry period is a time of hardship, for others 

 simply uncomfortable with its dust and desiccating air. In 

 these periods of long drought the skin becomes parched, lips 

 chap; the discomfort sets nerves on edge and teinpers flare. 

 There is no water for washing, it is too precious. In some 

 areas there may not be enough to drink. Arguments for 

 water rights are serious, sometimes fatal, and the nomads 

 with their livestock wander in constant search. But with the 

 coming of the rains, with water, browse and food again 

 available, people change. They relax their wanderings, 

 and it is easier for all to get along. For the nomadic herds- 

 men living in areas too dry to plant a crop, springtime is a 

 time for marriages, feasts, and settling debts. For these 

 people it is a short spring, a rainy period that ends soon and 

 then the wandering search for water and browse again be- 

 comes a serious task. 



With the continuance of rain and growth, spring passes 

 into summer. The rainy period with its cloudy weather and 

 cooler temperature is often called winter by English-speak- 

 ing people in the tropics, even though it is the growing sea- 

 son. In areas with a long and consistent wet period many 

 plants will flower at the end of the rains and into the short, 

 dry season. These areas do not exhibit the burst of flower- 

 ing foimd in regions with a short and less reliable wet season. 

 This sudden renaissance of growth that takes place in as 

 little as two weeks is characteristic of the drier tropics. It is 

 what I have called a tropical spring. 



APRIL Page II 



