A natomico-physiological. Relations in the Spermophyte Shoot. 147 
the most part free from hairs, the hypocotyl will almost certainly be devoid 
of hairs. If the free margins, more especially along their lower extent, are 
ciliate, then it is likely (though not inevitable, for the hairs peter out in 
some cases) that a hair line will be formed down each side of the hypocotyl. 
If the cotyledons are markedly hairy on the margins or the surface or 
in both regions, then we may expect that the hypocotyl will be hairy 
Fig. 25. A— 1 Ipomoea sanguined , showing the appearance of the hypocotyl as seen in transverse 
section at successive levels from above downwards ; a , epidermis ; 6, papillae, absent from 
the furrow ; c, outermost layer of the cortex, containing anthocyanin ; d , furrow ; e, endodermis ; 
f, fibro-vascular bundle. 
all over. That is to say, where hair formation is a normal feature of the 
free basal margins of the cotyledons we may find the same character 
exhibited along their potential edges. This is as far as mere outward 
examination of the hypocotyl will carry us. The determination of the 
morphological nature of the axial core is a more difficult problem. In 
seedlings of the Ipomoea type we have a typical stem arrangement of the 
vascular tissue (xylem and phloem superposed) throughout the length of 
the hypocotyl (see Fig. 35). The opposite extreme condition in which 
a root arrangement (xylem and phloem alternate) is found extending 
up the hypocotyl to the cotyledon node has been recorded by various 
authors. This alternate disposition may even come about in the petioles 
before the cotyledon traces enter the hypocotyl as has been described 
by T. G. Hill’ 1 in Piper cornifolium. A similar condition has been found 
by Tansley and Thomas 2 to exist in many members of the Rhoeadales and 
Ranales. In a detailed investigation of the vascular tissue in the seedlings 
1 The New Phytologist, vol. iii, 1904; also Ann. Bot., vol. xx, 1906. 
2 The New Phytologist, vol. iii, 1904. 
