736 
Lee.— Observations on the 
The behaviour of the internal phloem groups is interesting. While 
still in the petiole, the internal phloem undergoes equal division, one part 
going to each of the lateral xylem masses. In these positions, and with 
occasional anastomoses, the whole of the hypocotyl is traversed. Previous 
to entering the root, however, the two groups belonging to one midrib come 
together and fuse (Diagram 5, Fig. 4) ; then, passing to the centre, they join 
on to the group derived from the other cotyledon (Diagram 5, Fig. 5). 
Occasionally, anastomoses with the external phloem are seen. Finally, the 
fused phloem mass elongates in the intercotyledonary plane, bifurcates, and 
the two branches pass out right and left to join the external phloem (Dia- 
gram 5, Fig. 6). A little pith is present at this time, but this soon disappears, 
and a solid xylem core results (Diagram 5, Fig. 7). 
Many variations on this arrangement were found. The definite fusion 
and division of the internal phloem are not always so clear as has just been 
described. Fusion may take place irregularly, and one part may pass out 
and join the external phloem long before the other. In addition, the internal 
phloem masses are often more numerous than in the simple case described 
(cf. Gerard, 7 , p. 375). Blind endings are seldom found, and even when they 
apparently occur, it is only after anastomosis with another phloem mass. 
Datura Me tel, L. Seedlings rather larger than in D. Stramonium , 
and the details of transition are better shown than in the last species. The 
division of the midrib xylem into three is more definite, as is also the 
possession of protoxylem by the two lateral masses thus produced. One 
difference is noteworthy, though there are indications of the same pheno- 
menon in D. Stramonium , viz. the division of the internal phloem of the 
cotyledonary trace into three parts, one going to each of the three xylem 
masses. Anastomoses take place not only between the different internal 
groups, but also between the latter and the external phloem. In other cases 
the internal phloem groups were more numerous. The final result is the 
same ; all the internal phloem masses come together in the centre, the fused 
bundle divides, and the two parts diverge and join the peripheral phloem. 
Another peculiarity was seen in one specimen in which the three protoxylem 
groups derived from one cotyledonary bundle remained distinct for a long 
time after the root was reached (PI. LXVIII, Fig. 2). The lateral proto- 
xylems were at first stronger, but after a time they decreased in size and 
finally disappeared. The metaxylem became more compact, and the 
median protoxylem assumed the exarch position in the plane of the 
cotyledons. 
Nicotiana alata , Link and Otto. In this species the seedlings are very 
small, and the transition, which takes place in the upper part of the hypocotyl, 
is according to Type 3.' This species differs from the rest of the Solanaceae 
examined in the scanty supply of phloem, this tissue being entirely absent 
from the inner side of the vascular bundle, which, therefore, throughout the 
