656 Proceedings of Royal Society of Edinburgh. [sess. 
endodermis had quite lost its distinctive characters, and the im- 
prisoned cortex had all the appearance of a normal pith. At this 
stage the xylem bundles, which were of very different size, con- 
sisted of mingled larger and smaller tracheal elements, in which 
it was impossible to determine the positions of the protoxylems ; 
it was consequently impossible to say when the root arrangement 
ended, and that of the stem began. The positions, and also the 
numbers, of the bundles were always changing, due to fusions 
and divisions. 
Just before the ‘ collet ’ was reached, the bundles, after much 
shifting, arranged themselves symmetrically, and the section of the 
false stele was roughly a square, each side of which was occupied 
by a typical stem bundle with two protoxylems pointing to the 
centre, and the four angles each by a group of small xylem vessels 
(possibly protoxylem), which went off to lateral roots, and were 
lost (fig. 7 (b ) ). 
Above this plane the structure conformed to the type normal 
for the base of the hypocotyl, and the splitting of the four stem 
bundles gave the ordinary eight hypocotyledonary bundles. 
Arrangement op Bundles in the Hypocotyl. 
From the ‘ collet ’ the eight hypocotyledonary bundles pass 
upwards unbranched till within a few centimetres of the point 
of origin of the cotyledon petioles. The distance from the root 
at which the apparent branching takes place depends on the 
length of the hypocotyl. 
In a well-grown specimen the hypocotyl varies between 12 and 
25 cm. in length. 
In the case of a hypocotyl 15 cm. long, the original eight 
bundles remained unbranched to a height of 10'5 cm.; in one, 
14-5 cm. long, the first appearance of branching took place at 
about 10 cm. from the collet; and in the case described in detail 
below, the hypocotyl was 19 '5 cm., and branching first appeared 
at 13 cm. above the ‘collet.’ 
In every case the branching is perfectly regular up to within 
some few millimetres of the cotyledons ; higher up and in the 
epicotyl, although, in the main, the arrangement of bundles in 
