Seedling Anatomy of Certain Sympetalae . II. 309 
and joins on to one of the remaining lateral strands (Diagram 4, 11). At 
a still lower level in the cotyledonary tube, the remaining lateral bundles 
fuse in pairs, so that four equal vascular strands enter the hypocotyl 
(Diagram 4, III). Almost immediately, the xylem in each case becomes 
rearranged and the protoxylem assumes an exarch position, while the 
phloem groups, of which eight have been formed by division of the original 
four, fuse in pairs, and a tetrarch arrangement is produced (Diagram 4, 
IV and v). 
The root is long and fairly stout, and for the most part a large pith is 
present. This, however, becomes smaller as the apex is approached, but at 
no place does it disappear altogether. 
It may be observed here that, though the seedling is large, the transi- 
tion takes place at a high level in the comparatively short hypocotyl. 
Xanthium Strnmarium , Vahl. Seedlings generally a little larger 
(never less than 10 cm. long) than in Silphium perfoliatum , but possessing 
the same general characters. 
In the upper part of the seed-leaf the behaviour of the vascular bundles 
is the same as in Silphium perfoliatum . After division and subsequent 
re-fusion of the strands, there are present at the base of each cotyledon 
a large number of vascular bundles-— viz. a large midrib, two smaller laterals 
near the margin, and, in the intermediate positions, numerous still smaller 
bundles. In the large cotyledonary tube the midrib bifurcates, its proto- 
xylem becomes exarch, and the whole mass of vascular tissue assumes 
a form which it retains until the root is reached. 
The remaining strands pass unchanged into the hypocotyl. In the 
Y 
