Anatomico-physiological Relations in the Spermophyte Shoot. 143 
the outlines, or the whole may have a slight lateral skew. Such departure 
from an exact geometrical form may give rise to a deviation from the 
ordinary pattern, as is seen in Lopezia coronata (see Figs. 12 and 23). Here, 
although we have (as it seems) a §■ divergence in the upper part of the shoot, 
and an insertion width of ~ giving the expected five contour lines in each 
internode, these lines do not continue uninterruptedly down the stem, but 
terminate in the axil, some in the median line, some to one side of the 
axillary bud. Of the two lines arising at each insertion the shorter one, 
after being ‘ picked up 5 at the start by one descending from the neighbour- 
ing higher leaf, continues through three internodes ; the longer one descends 
through five, 4 picking up ’ one from a neighbouring lower leaf after it has 
traversed two (see later, p. 153 and Fig. 12). 
With a very wide leaf-insertion, as in Viola tricolor and allied forms, 
where it approximates to § of the circumference, the divergence being again 
J-, only two contours appear in each internode, the two formed by each leaf 
extending through only one and two internodes respectively (see Figs. 13 
and 17). In the flower spike of Mignonette ( Reseda odorata) we have 
a transition from a § to a § divergence. The bract-insertion being J of the 
circumference, we find the same uninterrupted continuity of the lines (here 
eight in number, see Figs. 14 and 16) as in the case of a | insertion with a 
§ divergence (see above). Contour relations of a like nature are also 
observed in the ultimate branches of the shoot axis, i. e. in the individual 
flower stalks. In Viola and Calystegia this is particularly clearly shown 
(see Figs. 17 and 19). Two bracts, large in Calystegia , quite small in Viola , 
accompany the flower, and are placed a considerable distance up the full- 
grown flower stalk. In both plants contour lines starting from the bract 
insertions are traceable to the base of the pedicel. As the portion of the 
stalk above the bract level elongates, - similar lines due to the outer sepals 
become visible in this region. In Reseda odorata the pedicels show longitu- 
dinal ridges and furrows, the number always corresponding with the number 
of sepals, which varies from four to as many as eight (see Fig. 16). 
Among Monocotyledons it is less easy to obtain the kind of evidence 
required for our present purpose. In this class the production in the seed- 
ling of a well-developed hypocotyl or in the adult plant of an elongated 
leafy shoot with a length of internode and width of leaf-insertion offering 
favourable conditions for the exhibition of those features which are easily 
demonstrated in Dicotyledons is exceptional. In the shoot axis of certain 
families (e. g. Commelinaceae, Gramineae, Dioscoreae), however, these con- 
ditions are fulfilled, and here we are able to see that the surface configura- 
tion depends upon the same relations as in Dicotyledons. 
In the Coniferae, on the other hand, there is abundant evidence that 
these relations hold, as, indeed, we might expect in view of the essential 
similarity of arrangement and development in this group and in Dicotyle- 
