A natomico-physiological Relations in the Spermophyte Shoot. 149 
out the internode from leaf junction above to mid-axil below, well developed 
even in the youngest internodes. 
Asclepias linifolia. Leaves opposite. Internodes with two conspicu- 
ous lines of hairs or with one line broad and well defined and the other narrow 
or even wanting. In the last-mentioned case the positions of the one line 
in successive internodes lie on a continuous spiral, as in Stellaria media (see 
below), though occasionally the direction is observed to become reversed 
§ven in unbranched stems standing erect. 
Stellaria media. Leaves opposite. Stem glabrous except for a single 
well-defined line of hairs extending from one of the two leaf junctions 
at each node to the mid-axil of the leaf immediately below. A cross- 
section of the middle region of the internode shows a ririg of four vascular 
bundles symmetrically disposed. The two in line with the midribs of 
the leaf-pair above are small ; the alternate pair occupy a more extended 
arc. It is exactly opposite one (or sometimes both) of these larger double 
bundles that the hairs arise (see Fig. 10). In each successive internode this 
line shifts through a quarter of the circumference, always in the same 
direction, so that it traces a spiral round the axis. The direction of the 
spiral may be either to the right or to the left, and may be in opposite 
directions in different branches on one individual. Among most of the 
plants examined the lowest internode on the chief axes was without this hair 
line ; sometimes this was the case also with the next one or more. Once 
having appeared, however, it continues almost without exception uninter- 
ruptedly up the stem. Now and again an internode may be found with a 
second hair line, sometimes weaker, sometimes as well marked as its fellow, 
starting from the other (opposite) leaf-junction. Attempts to relate the 
occurrence of two lines of hairs with any other external morphological 
feature proved unsuccessful. So far as appeared, the demarcation of the 
second leaf-extension fusion line in any internode was not directly related 
to the .degree of vigour of development, symmetrical or otherwise, of the 
axillary buds either at the node above or below. In other words, no 
expectation could be formed as to when two lines would be found. There 
is, however, some indication that a second hair line is more frequent 
in plants grown in dry soil and fully exposed to the light— a conclusion 
quite in accord with that arrived at in other cases. Certain other relations 
of the single, or of the more pronounced line if two are present, appear to 
be more strictly laid down. When this hair line appears on the lowest 
internode of a vegetative lateral axis it always occurs on the adaxial side, 
but the direction which the spiral will then proceed to take can only 
be ascertained by inspection of the next (second) internode. In the flower- 
ing region, where the axillary bud of both leaves usually develops, the 
main axis (the central flower stalk of each cyme) becomes pushed at each 
successive node to one side (a displacement which does not occur when both 
