INTERNAL TEMPERATURE OF LEAVES. 288 



For Mangifera indica (mango) I have the following notes : — 

 February : Every mango seen was in young leaf. 

 August : One tree recorded. 



September : A good many were noted in the district, 

 only three or four in the Gardens. 



For Theobroma Cacao — 



February : Very full of young leaf. 

 June : Fair amount, not general. 

 August : Fair amount. 

 September : Rather full. 

 November : Fair. 



For Ginnamomum' zeylanicum, a planter at Negombo — a 

 place which has similar incidence of monsoons and similar dry 

 periods to those at Peradeniya — informed me that on his 

 estate there were two certain periods for the " flush " of the 

 cinnamon, the most general one being in February, and 

 another somewhat less so in September. Besides these there 

 were occasional very partial irregular " flushes " in June and 

 July. Thus the evidence seems to point in these species to a 

 correspondence between the period of new growth and the dry 

 periods, the most general period for a large number of species 

 being February in the midst of the longest dry period occur- 

 ring in this part of the Island. Species which grow once a 

 year usually do it in February, species with two growth 

 periods usually grow in February and September, and species 

 with more frequent periods almost always have February as 

 one of them, and that usually the one in which the growth is 

 most general. 



Conclusions and Theoretical Suggestions from the 



Observations. 



This general result is somewhat surprising. The only pre- 

 vious results bearing on this point are those of Wright (32), 

 who has worked out the periodicity of deciduous trees in 

 Ceylon in a very thorough manner. His results are given on a 

 period of observation extending from 1900 to 1905. His 

 general conclusion is that the largest number of leafless species 

 coincides with tlie longest dry period of the year, namely, 



7(1)09 (37) 



