THE AMERICAN BOTANIST* 



93 



there are others. And they would have us to understand 

 that deciduousness among trees is a very complex and in- 

 teresting problem for botanists to work out. 



Mayaguez, Porto Rico. 



The editor takes the liberty of adding the following 

 notes on the "Foliar Periodicity in Ceylon" from the paper 

 by Herbert Wright read before the British Association for 

 the Advancement of Science last year. It will be seen that 

 Ceylon trees behave much as do those of the American 

 Tropics. 



In Ceylon, there is no relationship between deciduous 

 and allied species. The same genus may or may not con- 

 tain deciduous species, or as in the genera Terminalia^ 

 Picas, Stercnlia, Stereospermum, and many others, there 

 may be a very large percentage of the species deciduous. 

 Some natural orders, as, for instance, the Sapotace^e and 

 Ebenacese, are peculiar, in that only one or two species 

 are other than evergreen, and not a single natural order 

 can be quoted which has a high percentage of deciduous 

 species. Nevertheless, though this investigation is quite 

 young, I have obtained nearly 200 species of Ceylon trees 

 which pass through a deciduous phrase at recurring 

 periods of time. It is worthy of note that though differ- 

 ent specimens of the same species show every variability 

 in the period of time at which they drop their leaves and 

 produce new f oliage, yet the same tree passes through this 

 phrase at exactly corresponding times from year to 3^ear. 



In studying the behaviour of our deciduous trees the 

 most usual conclusion is that no law and order prevails, 

 and any tree drops its leaves how and when it chooses. 

 There are, however, certain features which point to a clim- 

 atic response, and others which indicate that the personal 

 or interval forces are the chief agencies at work. It can 

 be definitely stated that the majority of our deciduous 

 species show a response to climate, in so far that they do, 

 in climates similar to that prevailing at Peradeniya, drop 

 all their leaves and remain leafless during our hottest and 

 driest season. This hot dry period extends from January 

 April or May, and the leafless trees of Bombax mala- 



