INTERCELLULAR CANALS IN DICOTYLEDONOUS WOODS 437 



more often arranged in conspicuous narrow concentric lines, giving the 

 appearance of growth rings. That they are not growth rings is shown 

 by their very irregular spacing, and, what is more conclusive, by the fact 

 that they rarely form complete circles. The presence of distinct resin 

 rings proves that a specimen [of Philippine wood] belongs to this fam- 

 ily, but they are so irregularly arranged that a small specimen may often 

 be without them." 



The woods commonly known as Philippine mahogany (lauan, tan- 

 guile, tanguile mahogany, Bataan mahogany, etc.) belong to this family, 

 and the concentric rings or arcs of small canals with their whitish de- 

 posits afford a ready means of separation from other commercial 

 mahoganies, now of special importance for airplane propellers. 



Comhretacecc 



x\s previously stated, secretory cavities developed by the disorgtiniza- 

 tion of portions of the tissue of the wood have been reported for Tcrini- 

 nalia. 



In Terminalia catappa, from Hawaii, the writer has observed large, 

 well-defined secretory canals arranged in tangential series, and siiowing 

 the usual anastomosing character in tangential section. The surround- 

 ing cells are small and short, rounded on the side next to the cavity, 

 and show no wall fragments such as are seen in the case of Liquid- 

 amhar. They were first noted by Brown (13). 



Myrtacece 



Although secretory cavities occur in the leaf and in the ground tissue 

 of the axis of this family, the writer has been unable to find any refer- 

 ence to secretory canals or cavities in the wood. 



In the woods of Eucalyptus citriodora, from Plawaii, and B. pilitlaria 

 and E. macnlata, from Australia, the writer has found well-defined 

 gum canals extending throughout the length of the specimens (maxi- 

 mum about 0.3 meter). They are in a zone of parenchyma in a short 

 tangential series, with their greatest diameter radial, the largest meas- 

 ure 2 mm. across at the widest part. They anastomose very frequently, 

 and are partially filled with gummy substance. They are occasioned by 

 wounding, and while their mode of origin is unknown, they have evi- 

 dently enlarged lysigenously. 



Araliacece 



Only radial canals have been observed in this family. The w riter has 

 observed them in the wood of three representatives, namely. Chciro- 



