A natomico-physiological Relations in the Spermophyte Shoot, t 5 1 
of the leaf-extensions, although it does not cause any obvious displacement 
of the leaves themselves ; and (3) that exceptionally it may be sufficiently 
lessened temporarily as to do away with any outward effect of asymmetry and 
hence the two equal hair lines. This interpretation of the Stellaria con- 
figuration appears to be more consonant with the facts than the explanation 
offered by Eichler, 1 who considers that although the leaves are opposite and 
decussate, yet, since one member of the pair begins to develop a little earlier 
than its fellow, we should regard them as in fact spirally arranged with 
a leaf-divergence of To which conception we must presumably add the 
idea of a one-sided effect on the leaf-extension in order to account for the 
general absence of the hair line fro m one edge of the leaf-insertion. A 
similar one-sided disposition of the hair line is sometimes to be observed 
in seedlings. In some individuals of Cosmos bipinnatus , for example, a 
distinct line of hairs was present on one side of the hypocotyl, but ex- 
cept for two or three immediately beneath the point where the free 
margins of the cotyledons coalesced, the opposite side was destitute of 
hairs. Yet it surely would be somewhat fanciful on this ground to apply 
the conception of a % divergence to the cotyledons. In other species show- 
ing a difference between the two sides of the axis, the normal condition may 
be one in which this inequality is much less pronounced, as in the case 
where two hair lines commonly occur but the one is much weaker than the 
other (observed in seedling plants of Bidens ferulaefotia , D.C.). It has 
seemed necessary to dwell at some length on the case of Stellaria , since a 
mere statement of the facts without further analysis would make it appear 
that this configuration was not amenable to interpretation on the theory of 
the leaf-extension as here set fort h. 
Certain hairy-leaved species of Veronica . In V. hederaefolia, V. arven - 
sis, and V. polita , as well as in the familiar case of V. Chamaedrys , a 
definite hair pattern is exhibited when the plants are growing under cer- 
tain conditions. That this fact has hitherto only been generally recog- 
nized for V. Chamaedrys is due no doubt to the circumstance that in 
this species the hairs are of one kind, and that the rest of the surface 
is nearly' or quite glabrous ; whereas in the other species named the 
hairs are usually of two kinds, the one long, needle-like, and spreading, 
the other short and closely set, forming a sort of pile. Along the line 
of fusion of the leaf-extensions we find a tract covered with pile, but 
with few if any of the long hairs which are abundant over the rest of 
the surface. This appearance is particularly clear in V. hederaefolia . In 
this species the cotyledons and hypocotyl are frequently glabrous. Under 
suitable conditions, however, hairs develop on the margins of the petioles and 
extend down opposite sides of the hypocotyl in two vertical lines, petering 
out, it may be, before reaching the root, the rest of the surface being desti- 
1 Bliithendiagramme, II, p. 17. 
N 
