Structure of Acer Pseudoplatanus. 
575 
tance below the cotyledonary node the xylem of each of the four diagonally 
placed bundles divides into two, so that at this level there are eight groups 
of metaxylem associated in pairs, each pair lying within one large group of 
phloem (Fig. io). This arrangement of the vascular tissues is maintained 
Figs. 7—13- Series of semi-diagrammatic figures, showing the behaviour of the vascular strands 
during the transition from the cotyledons to the younger part of the root. Figs. 11 and 1 2 are from 
sections below the collet, and illustrate the leisurely manner in which root structure is attained. 
* 
Figs. 14-21. Fig, 14. Young seedling from which the sections illustrated in Figs. 15-21 were 
drawn. Fig. 15. Cotyledonary midrib. Fig. 16. Bifurcation of midrib. Fig. 17. Isolated protoxylem 
and one diagonal bundle at the top of the hypocotyl. Fig. 18. Portion of section from the middle of the 
hypocotyl : the xylem of the diagonal bundle has divided into two. Figs. 19-21. Successive stages 
in the formation of the cotyledonary root pole. Fig. 21 is near the lower limit of differentiation. 
(Figs. 15-21 x 600.) 
in the very young seedling to the lower limits of differentiation, thus showing 
that the bulk of the initial growth is intercalary in character. The epi- 
cotyledonary leaves, two in number, are very minute at this stage and show 
very little differentiation of tissues. At the cotyledonary node six desmogen 
strands are present in the intercotyledonary plane, these being in two groups 
Qq 
