450 Arber. — On the Leaf Structure of certain Liliaceae , 
in some little detail. Asphodelus liburnicus , Scop. (Asphodeline liburnica , 
Reichb.), may be taken as an example of those species of Asphodel which 
have a more or less centric type of leaf ; the mature limb is roughly 
triangular, but with an extra ridge in the median line of the adaxial (upper) 
surface — the base of the triangle — and subsidiary ridges between the four 
main angles (Fig. n). The leaf structure is best understood from the con- 
sideration of serial sections through an apical bud, such as that represented 
in Fig. 9. The section is taken below the level of attachment of leaves 1, 
2 , and 3, and their vascular supply is still included within the axis. In the 
case of each leaf, there is, from the beginning, a median bundle, m.b ., and 
a lateral on either side, l x and / 2 . Leaves 4 and 5 are free from the axis, 
but their membranous wings form a closed sheath round it. In the suc- 
ceeding leaves the sheath, though still a conspicuous feature, is open ; the 
closed region is thus extremely short. In leaves 5 and 6 the midrib bundle 
is in the act of branching, and in leaf 7, and all successive leaves, the 
vascular strand, i.b., which it gives off, is entirely free. As is shown in 
Fig. 9, the bundle, i.b., is sometimes derived from one side of the median 
strand and sometimes from the other, in a way that seems to be quite 
fortuitous ; I have not been able to discover that there is any regularity or 
rhythm in the right-handed or left-handed origin of this strand in successive 
leaves. But, whether it be given off to one or other side, the bundle in 
question gradually moves round and eventually places itself opposite to the 
median bundle, towards the xylem of which its xylem is turned. We meet 
with a similar case in the median bundle of the leaf of Tritonia (Iridaceae), 
which also gives off a lateral branch which immediately takes up an inverted 
position, but here the parent bundle and its branch remain in close association 
and form a double bundle (Arber, A. ( 1918 ), Fig. 1 5, p. 483). 1 In Asphodehis 
liburnicus each of the lateral bundles (l v / 2 ) gives off a branch ( 7 / and / 2 r ) 
which lies towards the lower surface of the leaf between the midrib and the 
lateral angles (Fig. jo). The adaxial bundle, i.b., gives rise in many cases 
to two branches {i.b! and i.b."), so that there are three inverted bundles 
towards the upper surface of the leaf (Fig. 11). An example of an anomaly, 
which occasionally occurs, is seen in leaf 13, Fig. 9. Here the median 
bundle gives off two inverted bundles, i.b. x and i.b.%, instead of the single 
bundle, i.b. 
It will be observed that in A. liburnicus the region which is ana- 
tomically of leaf-base nature is very short, as the inverted adaxial bundle 
quickly comes into being, thus rendering the vascular symmetry rather 
petiolar than ‘ leaf-base ’ in character. This reduction of the leaf-base is, as 
we shall see, carried still farther in Eremurus. 
The leaves of plants belonging to the genus Asphodelus are not all 
1 
1 Chodat, R., and Balicka-Iwanowska, G. (1892). The present writer has confirmed these 
authors’ description of the origin of the double bundle. 
