The Origin of the Seed-Leaf in Monocotyledons. i i i 
clear at once from the figures in this paper and the accompanying 
descriptions. My own examination of Eranthis draws tne parallel 
even closer. The two series of diagrams placed side by side on 
Plate (figs. 2-6 and 8-12) show an astonishing likeness in the 
arrangement and course of the bundles which traverse the transi¬ 
tional regions in the two species figured. 
The cotyledons in an Eranthis seedling of the age shown in 
fig. 7 are united for the greater part of their length. Their blades 
are distinct, but the long petioles form a slender cylinder, solid just 
beneath the blades and again in the region above the stem-bud, but 
hollow between those levels (fig. 8), and opening out again into a 
conical chamber over the tuber. Within this hollow is the very 
small stem-bud, seated on the tuber, and completely enclosed within 
the cotyledonary tube (fig. 9). 
Three bundles from each cotyledon enter the petiolar cylinder, 
but very near the top of it the two lateral traces from each blade 
unite with their own midrib. From this level downwards the 
petiolar cylinder contains two massive bundles, each representing a 
separate cotyledon (cf. Sterckx, loc. cit., PI. xix., figs. 250, 251 
and others). 
The section which passes through the stem-bud shows each 
cotyledonary bundle opening out into two in a characteristic way 
(fig. 9). The two halves separate like two flaps of a screen, the 
protoxylem group representing the hinge. The insertion of the 
little-developed plumular traces on those of the cotyledon does not 
affect the symmetry of the transition. As we descend in the tuber 
every trace of this insertion disappears. Each cotyledonary trace 
opens out until the stage shown in fig. 10 is reached. There are 
now four distinct bundles of the stem-type in the hypocotyl, 
arranged in pairs at either extremity of one diameter. 
Following the series of sections downwards, all the traces 
become more widely separated as the tuber increases its girth, for 
they keep near the periphery. As each pair of bundles separates 
three xylem groups are formed: one within each of the two phloem 
groups, and a third half-way between them. This median xylem 
group finally divides, and then we have the structure shown in 
fig. 11. Four phloem and eight xylem groups are arranged at fairly 
regular intervals round the periphery of the tuber, which has now 
almost reached its maximum diameter. As it narrows again 
towards the base, the xylem collects into four masses. The arrow¬ 
heads in fig. 11 point out how this takes place. The four phloem 
