Anatomico-physiologieal Relations in the Spermophyte Shoot . 155 
dahurica , which we may take as an example, the leaf-divergence is f and 
the insertion width between \ and -J, hence, as explained above (p. 140) and 
as shown in Figs. 18 and 19, no actual ‘pick-up’ occurs. Each contour 
ridge runs a separate course through two or three internodes according 
as it starts from one side or other of the insertion, and the two adja- 
cent lines from neighbouring leaves (one from the right edge and one 
from the left) terminate in each axil. We thus get five contour lines 
in each internode. The stem is coloured with anthocyanin, and this is 
ordinarily confined, as in the seedling, to the layer beneath the epidermis, 
where most of the chlorophyll is also located. A cross-section through 
the middle of the internode (see Fig. 27) shows a ring of five vascular 
bundles, each extending through a considerable arc midway between two 
ridges. The second and succeeding layers of the cortex become con- 
verted into collenchyma, and the whole central tissue of each ridge may 
be thus thickened, but the outermost layer containing the anthocyanin 
remains unchanged. At the crest of the ridge, however, i. e. along the line 
of fusion of the leaf-extensions, there is frequently a gap of one or two cells 
in the anthocyanin ring, just as there occurred a similar break in the furrow 
(fusion line of the cotyledon extensions) of the hypocotyl in Ipomooa (see 
above, p. 138, and Fig. 25). When this is the case these colourless junction 
cells may undergo collenchymatous thickening as well as those lying deeper. 
The same 4 potential edge 5 character is thus common to the furrow of the 
hypocotyl and the ridge lines on the stem. The axillary flower stalk is 
marked by similar contour ridges, due in the lower region to the down- 
ward extensions of the two bracts and in the upper portion to those of 
the outer sepals (see Fig. 19). The petioles are stout and channelled, 
and their insertion, owing to their angular outline, gives rise to special 
trace lines which form a subsidiary pattern within the larger configura- 
tion. Such subsidiary patterns are not infrequently present when the 
petiole is four-angled, as is seen in Rivina humilis , especially if the leaf 
is large and compound, as e. g. in Phaseolus multiflorus . 
Viola tricolor . Leaf-divergence §, leaf-insertion width about f. The 
stem shows two well-marked contour ridges in each internode. Of the two 
arising from each insertion one descends through only one internode, the 
other through two (see above, p. 143, and Figs. 14 and 17). As is the 
case in Calystegia , the flower stalk exhibits ridge lines due to the two 
bracts, minute as they are, which are placed some distance up the pedi- 
cel. As the region above the bract level elongates, similar lines arising 
from the posterior sepal can be traced passing between the bracts (which are 
not near enough together to furnish a 4 pick-up ’) along the whole length of 
the flower stalk. 
Reseda odorata. Leaf-divergence in the vegetative axis •§, leaf-insertion 
width between f and f. General scheme similar to that of Calystegia (see 
