638 Sargant .— 77 ^ Vascular System of Seedlings. 
EXPLANATION OF FIGURES IN PLATE XXXIII. 
Illustrating Miss E. Sargant’s Paper on A New Type of Transition from Stem 
to Root in the Vascular System of Seedlings. 
Fig. 1. Outlines of two of the seedlings cut (A x and A 3 ). The apex of the 
cotyledon is still hidden within the seed in A x . The numbered lines drawn through 
the outline of A 3 refer to the following figures; thus the hand-section drawn in 
Fig. 2 was cut about the level marked 2 in the outline drawing. Life size. 
Fig. 2. Hand-section through upper part of cotyledon ( A 3 ), showing the two 
massive bundles within it. The orientation of this section does not correspond 
with that of the series from which Figs. 3-6 were drawn, x 75* 
Figs. 3-6. Four successive sections from a microtome series through the region 
marked 3-6 in Fig. 1. The orientation is uniform in all, and the lettering as 
follows:— 
M , M' .cotyledonary bundles. 
A .midrib-trace of first leaf. 
Ph x , Ph 2 .branches of phloem-group belonging to bundle M. 
Ph(, Ph 2 .branches of phloem-group belonging to bundle M'. 
px \, px 2> px 3 .protoxylem-groups derived from bundle M. 
px i} px u px x .protoxylem-groups derived from bundle M'. 
Fig. 3. Base of stem-bud, showing embryonic first leaf and growing point 
completely enclosed within base of cotyledon, x 75. 
Fig. 4. -34 m.m. below Fig. 3. Lateral traces of first leaf are fusing with M 
and M' respectively. Midrib-trace ( A ) is dividing and will, shortly follow the 
lateral traces. The phloem-groups of M and M have each divided; the proto¬ 
xylem-groups are as yet undivided and external, x 75. 
Fig. 5- -3 m.m. below Fig. 4. Central cylinder only, more highly magnified. 
Plumular traces have fused with cotyledonary traces. Three groups of protoxylem 
in each cotyledonary trace, becoming external. x 200. 
Fig. 6. .35 m.m. below Fig. 5. Transition nearly over. The central cylinder 
is surrounded by an endodermis. Three external groups of protoxylem are in situ ; 
the fourth is not yet complete ( px 2 , pxj). Four groups of phloem alternate 
with the xylem-groups. x 200. 
