HYPOCOTYL IN THE GENUS LUZULA. se 
show the thickening of their exterior walls so often seen in 
epidermal cells, and are in fact quite similar to those situated 
further within the tissues; no root-hairs or other outgrowths are 
anywhere produced by them. Within the endodermis an arrange- 
ment, quite like that of a root, is observable, and in all but one of 
the sections examined a diarch symmetry was seen (Fig. 10). The 
exception was a seedling of L. campestris, DC., where a faintly 
developed third xylem and phloem were noticed (Fig. 9). 
In passing downwards from the section described no difference 
is visible, and the vascular system passes into the primary root, 
apparently without any alteration except a distinct narrowing of 
its area just as it reaches the region where the collar of fixing 
hairs arises. 
Passing upwards, we find that the xylem and phloem become 
more and more difficult to determine, but continue to occupy the 
Same relative positions so long as they can be distinguished (Fig. 
15). The endodermis remains very obvious, and no other change 
is seen till quite close to the upper limit of the hypocotyl. Then, 
quite suddenly, there become evolved from the mass within the 
endodermis three separate bundles, one larger than the other two 
(Fig. 14). Next, the marked endodermis disappears from the 
side of the stele next the largest of these bundles, while the 
other two become somewhat oval in outline (Fig. 13). This 
point marks the upper limit of the hypocotyl, for immediately 
above it we find the largest bundle passing to the side into the 
cotyledon, now seen (Fig. 12) partly attached to and partly 
sheathing the shoot, into which the two oval bundles have passed, 
each dividing into two in doing so, and giving rise to four 
bundles lying near its centre. A little higher still, where the 
cotyledon has become quite separated from the shoot, we find 
these four bundles more separated from one another (Fig. 11). 
It would thus appear that the structure of the stele in the 
elongated hypocotyl of Zuzula is typically that of a diarch root 
throughout almost the whole of its course. Many similar 
hypocotyls have been described, especially amongst Dicotyle- 
dones by Hill (4), Tansley and Thomas (5), and others; while 
Miss Sargant (6) has pointed out that amongst Monocotyledones 
the transitional region between stem and root is always of 
extreme shortness, in her experience rarely reaching a length of 
