LEAF-FALL 453 



continuous ; buds may be formed, which open immediately 

 without a rest period. Resting buds may be formed early, 

 as in the beech, or at the end of the season. Resting buds 

 may open during the summer, normally as in the " Lammas 

 shoot," or as the result of leaf-fall following very dry, hot 

 weather, or after artificial defoliation, e.g. in the ash and 

 beech. 



This formation of resting buds, which open normally 

 only in the following spring, and the consequent period of 

 rest, has been ascribed by some authors, e.g. Schimper, to 

 an inherent and inherited rhythm. That this does not 

 determine the annual periodicity is, however, clear from the 

 behaviour of oaks, beeches, and other trees transplanted to 

 the more uniform conditions in the tropics ; of the tulip 

 tree and oak at Tjibodas in Java, Schimper says that they 

 " reflected winter, spring, and summer on their separate 

 boughs " ; some branches are leafless, some show young 

 leaves or unfolding buds, others have mature leaves. This, 

 Schimper holds, demonstrates an inherent periodicity of 

 growth which is no longer regulated by a definite seasonal 

 climatic cycle. Native tropical trees of the rain forests, 

 where conditions may be very even throughout the year, 

 rarely show continuous growth or a regular succession of 

 unfolding leaves. The conditions have been investigated 

 principally by Wright (1904) for Ceylon, and Volkens 

 (19 1 2) and Simon (19 14) for the more uniform climate at 

 Buitenzorg in Java. A number of trees are deciduous, but 

 in general the leafless period is short, and the leaves usually 

 fall more than once in the year. That leaf-fall is not directly 

 dependent on climatic conditions is shown by the fact that 

 in many cases different individuals of the same species lose 

 their leaves at different times. Thus Ficiis fulva sheds its 

 leaves two or three times in the year, standing bare for one 

 to two weeks. Of seven individuals observed by Volkens, 

 No. I and No. 7 were bare on the 20th of January, No. 2 end 

 of January, No. 3 and No. 5 middle of March, No. 4 end of 

 February, No. 6 beginning of June. Most trees are ever- 

 green, but only rarely, e.g. in Albizzia and Morinda, was 



