50 Wisconsin Academy of Sciences, Arts, and Letters. 



are deciduous like some species of Leguminosae, Guttifereae and 

 Ki. -us. On the other hand it is noted that a seven-year-old tree 

 of Theobroma Cacao had developed 22 radial-growth rings, and 

 since it cast its leaves three times a year it is evident that the 

 number of rings corresponded with the vegetative seasons of the 

 tree. The real cause of zonation is thought to be an inherent 

 characteristic of a plant though the environment induces its 

 manifestation. 



According to Dingier 103 leaf-fall is more dependent on the age 

 of the leaves than on the environment, for by cutting back decid- 

 uous trees in Ceylon some time before the normal period of leaf- 

 fall the new crop of leaves which immediately came out was re- 

 tained throughout the dormant season which is dry and very hot. 

 Unfortunately the effect upon radial growth was not noted but 

 from evidence given above it seems very likely that the periodic- 

 ity of radial growth always follows foliar periodicity in decid- 

 uous trees whether natural or induced. 



In another paper he 104 reported that the folier periodicity of 

 European fruit and forest trees grown in the highlands of Cey- 

 lon is very irregular even in different branches of individual 

 trees. In late October the trees of Quercus pedunculata could 

 be divided into five classes in regard to the condition of their 

 foliage, ranging all the way from cases in which chiefly old 

 spotted leaves were present (though some scattered buds were 

 swelling) to instances where no old leaves were present and the 

 new shoots occurred in all stages of elongation, although most of 

 them were full grown. Qucrcus Ccrris had a more uniform 

 periodicity. In late October all trees bore two generations of 

 leaves : the old ones hard and spotted, althought still green, and 

 the young ones not yet full grown. In late November the old 

 leaves had practically all fallen and the new elongation growth 

 had been completed. European pears, peaches, cherries, plums 

 and apples were found to have practically the same periodicity, 

 producing two crops of leaves and flowers, though but one crop 

 of fruit per year. The trees are often almost leafless some time 



' Dingier, H. Versuche iiber die Periodizitat einiger Holzgewachse 

 in den Tropen. Sitzungsber. Math.-Physical. Kl. Kgl. Bayer. Akad. 

 Wiss. Miinchen. 1911:127-43. 1911. 



M Dingier, H. tiber Periodizitat sommergriiner Baume Mittele- 

 uropas im Gebirgesklima Ceylons. Sitzungsber. Math.-Physical. Kl. 

 Kgl. Bayer. Akad. Wiss. Miinchen. 1911:217-47. 1911. 



