26 ORR—LEAF OF PICEA BRACHYTYLA, PRITZEL. 
portions of this incomplete septum, the projecting parts become 
united, and the division of the resin passage longitudinally is ac- 
complished. ‘This stage is represented in Fig. rb. 
The paired resin ducts, separated only by the septum, remain 
in close contact with each other, running parallel through the 
leaf for about one third of its length; but beyond this point, the 
secondary ducts diverge in a lateral direction, away from the 
parent ducts, and in successive sections cut through this region of 
the leaf, it is possible to trace their course outwards to the 
margin, where they ultimately die out, about midway between the 
base and apex of the leaf. 
The two main resin passages are continued almost to the apex, 
and transverse sections of the upper half of the leaf present the 
normal arrangement seen in the leaves of other flat-leaved Piceas, 
except that in one case a small lateral duct was observed near the 
apex, midway between the main duct and the leaf margin, but it 
only extended for a very short distance. 
Why the leaves of Picea brachytyla should possess this peculiar 
feature of paired resin ducts it is not easy to say; but it is a 
structural phenomenon which has every appearance of being con- 
stant in the species, and, so far as is known, it is not found in 
any other species of Picea. 
While it is recognised that in many plants anatomical differ- 
ences have a questionable taxonomic value, yet in the genus A bies, 
the position of the resin canals in the leaf is often made a deciding 
factor in the identification of a species, and it is suggested, on this 
analogy, that the unusual arrangement of the resin ducts in the 
leaf of Picea brachytyla might also be used with advantage as an 
aid to diagnosis in doubtful cases. 
