Chap. II] PERIODIC PHENOMENA IN THE TROPICS 253 



tropical dry seasons in the savannah-forests of Venezuela. Most of the 

 trees were leafless during my visit in March, 1883 ; not a trace of 

 vegetative activity was visible on them, and yet many of them, in particular 

 species of Cassia and other Leguminosae, were completely covered with 

 flowers. Epiphytic bromeliads and orchids were also in full blossom. 

 On the other hand, the vegetation on the ground was almost flowerless ; 

 it was however chiefly composed of grasses and other herbaceous plants, 

 the plastic substances of which accumulate chiefly in the foliage and 

 consequently must be expended for the production of flowers during the 

 vegetative season, that is to say, during the rainy season. In March their 

 foliage was as dry as straw. 



A show of flowers often even richer, particularly of perennial herbs, 

 accompanies the first rain after the dry season. But this continually 

 decreases as the rainy season proceeds, especially as regards woody and 

 tuberous plants, and sinks to a minimum at the close of the rainy season ; 

 whilst the growth of the foliage-shoots still continues for a long time, 

 the secondary growth in thickness attains its greatest intensity, and 

 assimilation as well as other nutritive processes are at a maximum. 



The fruits of many woody plants that have blossomed in the dry season 

 ripen during the ensuing rainy season ; others require a longer time. 

 Yet the ripening season for most fruits, so far as it is confined to any 

 particular season, appears to be chiefly the rainy season. Accordingly 

 there is very little fruit during the dry season. 



The favourable influence of the dry season on flowering is not at all 

 surprising. On the contrary, it is more a matter for surprise that certain 

 species of plants should blossom at the height and towards the end of 

 the rainy season. Such species are however very much in the minority, 

 especially when only woody plants are taken into consideration. It has 

 been shown in a former chapter T that poverty of water in the soil and in 

 the atmosphere favours the inception and growth of flowers. Blossoming 

 in the dry season, or soon after it, is a phenomenon that is intelligible on 

 physiological grounds. Why on the contrary it should in other cases, 

 rare however, be induced by the great humidity of the rainy season, 

 may perhaps be correlated in the case of woody plants with certain 

 adaptations, for example with special pollinating agents and the like. 

 That, however, many herbaceous plants without persistent stores of reserve 

 material should blossom during the rain, is a necessary consequence of 

 the direct dependence of the flowers on the foliage. 



iv. SPECIAL CASES. 



In order to obtain reliable and sufficient results regarding the influence 

 of the tropical seasons on the formation of flowers, I have collected from 



1 See p. 26. 



