CHAPTER II 



THE PERIODIC PHENOMENA OF VEGETATION 

 WITHIN THE TROPICS 



I. General Prevalence of Periodic Phenomena in the Functions of Plants. No 



isokite period of rest. Rest only for some processes. Occurrence of [jeriodicity in 

 opical vegetation. 2. Periodicity in the Vegetative Domain. \. Leaf -fall. Frequency 



periodic leaf-fall within the tropics. Diversity in appearance of trees during the dry 

 asons. Seasons of the year and vegetation in the campos. ii. Groivth. Periodic 

 .•foliation in certain species independently of the season. Individual periodicity of the 

 parate shoots of many tropical plants, iii. Temperate Woody Plants in the Tropics. 



Periodicity in the Sexual Domain, i. General Considerations. Separation in 

 )int of time of vegetative and reproductive activity, ii. Constantly Humid Districts. 

 on-contemporaneous flowering of different twigs in woody plants. Simultaneous flower- 

 g of all individuals of a species without relation to the season of the year. Connexion 

 tween formation of flowers and leaf-fall. iii. Periodically Dry Districts. Abundance 



flowers in the diy seasons and at the commencement of the wet seasons. Poverty in 

 •wers at the height of the wet season. The wet season the period for ripening fruit. 



Special Cases. Climate and flowering season in Java, in Nortli-west India, in Ceylon, 



British Guiana. 4. The Caesalpiniaceae in the Botanic Garden at Buitenzorg. 



. GENERAL PREVALENCE OF PERIODIC PHENOMENA 

 IN THE FUNCTIONS OF PLANTS. 



The periodic phenomena of tropical vegetation have hitherto been 

 vestigated onl>- to a sHght extent. As a result of the scant}- and usually 

 correct data supplied by travellers, the notion has been pretty generally 

 .■^seminated that in constantly humid tropical districts vegetative and repro- 

 ictive activity proceeds without interruption, whilst the well-defined dry 

 asons of other districts cause their vegetation to undergo periods of rest. 

 Observations in tropical districts with abundance of rain at all seasons 

 the year have taught me that there also vital processes in plants exhibit 

 ifhytliviic alternation of periods of repose anct of activity. This opinion, 

 iwever, depends on a conception of periods of rest that differs from the 

 ual one. 



The more recent investigations, especially those of Sachs and Muller- 

 lurgau, have proved satisfactorily that there are no periods of rest for the 



