423 
name implies, the whole bark is shed periodically. In this respect it re- 
sembles the closely related Hucalypti. In other genera of Myrtaceae the 
bark becomes papery. In Hugenia luzonensis the corky layer, which 
is a light red, peals off in this papery fold very much like the birch. In 
Eugenia bordenii the thin layers are light gray instead of red. While 
gray or brown are the predominating colors of barks, yet there are excep- 
tions. In Diospyros pilosanthera and other species it is nearly black. 
A yellow bark distinguishes Calophyllum wallichianium at once. In 
many cases the bark is ridged. Usually the ridges are low and corre- 
spondingly the depressions are shallow. Of course, in many species the 
rough barks do not appear until the tree has attained some degree of wa- 
turity. Among these trees which have rough barks may be mentioned 
Palaquium luzoniense, Anisoptera vidaliana (in very old age), Shorea 
contorta, Koordersiodendron pinnatum, and others. In Pithecolobium 
acle and in Bischofia trifoliata the corky layer consists of choppy flakes 
turning outward at the free, lower edge. 
Sap of bark.—Aside from the outer, the middle and inner barks often 
have distinctive characteristics which enables one to place them in the 
family. In the case of the Anonacee the strongly marked, medullary 
rays of the inner bark form alternating bands parallel with the radii of 
the trunk. The exudation of sap from the cut bark also is often striking, 
and with or without other characteristics will enable one to identify the 
families. Thus, in the Myristicacee represented by Myristica and Knema, 
the bark when cut freely exudes a red sap. In the genera Calophyllum 
and Garcinia of the Guttifere the sap is yellow. In the Dipterocarpacea 
a nearly colorless resin is slowly exuded. In the Burseracee, in species 
of Canarium and in Santiria nitida, a similar resin is found which burns 
readily. The white and often abundant milky sap of the trees in members 
of the Moracew, Apocynacee, and Sapotacee will distinguish these fami- 
lies from others, though often other characters are necessary to tell them 
one from the other. 
It will be seen from the above that frequently there are family, generic, 
or specific differences substantial enough to warrant the collecting of 
data for a key which will enable one to distinguish the many species by 
bark characteristics. Undoubtedly,.the need of such a key for the prac- 
tical forester is great, for the difficulty of obtaining flowers or even 
leaves from the tall trees, coupled with the multiplicity of species, makes 
the task of mere determination a difficult one. 
Cauliflory.—Schimper ** associated cauliflory with thin bark characters. 
Other authors associate it with conditions of pollination. Buscalioni *° 
claims that the cauliflower habit is a primitive one and persists in plants 
of hot, moist regions. The ecological advantages are numerous. In 
SL. ¢. 336. 
*® Busealioni, L., Sulla cauliforia. Malpighia (1904) 18: 116-176. A full 
bibliography of the subject is given with this paper. 
