50 Wisconsin Academy of Sciences, Arts, and Letters. 
are deciduous like some species of Leguminosae, Guttifereae and 
Ficus. 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- 
fail 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 w T here no old leaves were present and the 
new shoots occurred in all stages of elongation, although most of 
them were full grown. Quercus Cerris 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 
los Dingier, H. Versuche iiber die Periodizitat einiger Holzgewachse 
in den Tropen. Sitzungsber. Math.-Physical. Kl. Kgl. Bayer. Akad. 
Wiss. Miinchen. 1911:127-43. 1911. 
104 Dingier, H. uber Periodizitat sommergriiner Baume Mittele- 
uropas im Gebirgesklima Ceylons. Sitzungsber. Math.-Physical. Kl. 
Kgl. Bayer. Akad. Wiss. Miinchen. 1911:217-47. 1911. 
