ioo; 
Multi seriate Ray of the Dicotyledons . 
In this species, then, almost the whole of the woody cylinder possesses only 
uniseriate rays ; the multiseriate ones occur only in association with the 
leaf-trace and arise by the dissection of compound rays. 
A similar condition is found in Ledum groenlandicum (Oeder) and is 
represented in Fig. 3. Only one side of the woody cylinder is shown, with 
the edge of the pith at the extreme bottom of the figure. The horizontal 
spreading of the multiseriate rays with the increase in diameter of the stem 
is almost diagrammatic. Following the breaking up, the resulting rays 
may widen by their own growth and split again. The tangential view is 
given in Fig. 4. This section was taken further from the pith than Fig. 2, 
and consequently more horizontal spreading of the rays has taken place. 
As in Rhododendron punctatum , all the multiseriate rays in the stem arise 
in association with the leaf-traces. 
An important additional step is seen in Fig. 5, which is a photograph 
of a section of Kalmia angustifolia (L.), at the nodal region. In this 
species three traces arise at approximately the same level. One of their 
corresponding large rays is seen unbroken at the lower left of the figure. 
Above and at the lower right the breaking-up process has taken place. 
The result is that considerably more multiseriate rays occur in the adult 
wood than in the aforementioned species. Furthermore, at the right of the 
figure are to be seen two multiseriate rays which are not associated with 
the others. A series of sections would show, however, that in reality these 
are associated with a leaf-trace of a lower node.- As may be seen in the 
tangential section (Fig. 6), the group of rays extends for a long distance 
above the trace, in fact up to and beyond the next trace. This overlapping 
of the groups of rays gives the appearance in question and assists in dis¬ 
tributing the multiseriate rays throughout the wood. Another important 
fact in this connexion is that the groups of rays in their course outward 
through the wood extend continually higher vertically, so that in a tan¬ 
gential section as far out as the bark they are much higher than in one at 
the pith. 
Still more conspicuous overlapping and vertical extension of the rays 
may be observed in Chaemadaphne calyculata (Moench). In this species 
and in Kalmia angustifolia it is often difficult to observe the solid oak type 
of ray even at the pith. This stage is apparently omitted, the multiseriate 
rays often arising in a group from the pith above the leaf-trace. 
In other species of the Ericaceae, for example in Vaccinium corymbosum 
(L.), multiseriate rays may be found which are not in association with the 
leaf-trace but which arise quite independently at the pith or in the wood. 
The natural inference is that the habit of forming multiseriate rays, 
arising as indicated, has become firmly fixed upon the cambium, which may 
then form this type quite apart from the influence of the leaf-trace. The 
uniform distribution of the multiseriate type throughout the wood will then 
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