ORR—LEAF OF PICEA BRACHYTYLA, PRITZEL. 25 
in place of the usual two, and that these were in pairs, occupying 
the normal position belo the lower epidermis (Fig. 1a). The 
outer duct of each pair was slightly smaller than the inner one, 
and both were surrounded by moderately thick-walled cells, con- 
tinuous with the hypoderm. These “‘twin’’ resin ducts gave to 
the leaf section a very striking appearance, forming a marked 
contrast to the normal arrangement found in all other flat-leaved 
Spruces. 
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Fic, 1,—(a) Diagram of a Fonrreni age see of a leaf of Prcea brachytyla, showing the 
pai resin ut 3 
(b) Transverse a of a resin aoer: showing the origin of the secondary 
duct. s, the septum.. x a 
In order to test the constancy of this feature, and thereby form 
an estimate of its possible value as a specific indicator, similar 
preparations were made from the leaves of a herbarium specimen 
of a native plant of brachytyla, collected by Wilson in Western 
Hupeh, and bearing the number 1896. Here, as in the cultivated 
plant, a similar duplication of the resin ducts was observed. An 
examination of the leaves of a fruiting specimen grown in Ireland 
furnished additional evidence of the universality of the phen- 
. omenon, while indicating further that it is not confined entirely 
to the leaves of non-fruiting branches. 
Unfortunately, it was not possible to extend the investigation 
to include the type and co-types of the species, as these were not 
available ; but in the leaves of all plants that were examined, the 
doubling of the resin passages had taken place, forming an unmis- 
takable feature of the transverse section. 
The morphological origin of these secondary resin ducts is 
interesting and has been worked out in detail by means of serial 
sections. In those sections cut across the leaf immediately above 
its constricted base, only two resin passages were visible; but at 
a point about 1 or 2 mm. distant from the base, the outer, 
secondary ducts take their origin from the primary ducts by a 
process of division. ‘The first indication of this division is the 
production of a partial septum, formed by the elements of the 
epithelial layer, which have extended inwards at two points. By 
the subsequent growth in length of the cells composing the two 
