194 
Hill and de Frame. — On the 
large bundles (c. i-c. 4) give off branches of phloem and xylem which 
follow the path taken by the plumular tissue and reinforce it as it were. 
Hence, although these plumular bundles are marked p in the Diagram, in 
order to indicate their nature, it must be understood that at levels below the 
second figure of Diagram 7 they contain also vascular elements derived 
from the cotyledonary strands. During these changes the original bundles, 
c. 1, c. 2, c. 3, and c. 4, have each divided up into three ; thus c. 1 gives 
origin to c. 5 and c. 6, c. 6 again dividing to form c. 15 and c. 16 ; on the 
other hand, c. 4 divides directly into three, namely c. 10, c. n, and c. 12 
(Diagram 7, Figs. 3 and 4). At this level (Diagram 7, Fig. 4) the plumular 
bundles are clearly defined* and form a zone surrounding the cotyledonary 
ring of bundles ; that is to say, a similar anomaly of scattered bundles 
obtains in the hypocotyl as in the stem, although arrived at in a different 
way. Amongst the smaller cotyledonary bundles there is a general move- 
ment outwards so that they ultimately come into line with the plumular 
traces ; c. 9, c. 11, and c. 15 are among the first to show this tendency, and 
in so doing fusion with certain plumular strands may take place. For 
instance, the two small bundles immediately above c. 15 (Diagram 7, Fig. 5) 
join together and then fuse on to f. 15 ; also p. 5 and c. 11 effect a junction. 
Meanwhile the centrally placed cotyledonary bundles show changes, the 
most interesting of which are the formation of bicollateral structures which 
result from a strand of xylem passing from the normal wood to a position 
on the outer side of the phloem. For example, in c. 7 such a strand passes 
between this bundle and c. 16 outwards, and rests on the outer side of the 
phloem (Diagram 7, Figs. 4, 5, 6, and 7). On the opposite side of the axis 
the corresponding xylem is derived from c. 13,, and comes to rest on the 
adjacent bundle, c. 12. This appears to be the usual mode of origin of 
the abnormality, but exceptions occur; thus in another example of M. longi- 
folia it was, on one side only of the axis, arrived at in a modified way. In 
Diagram 7, Figs. 12 and 13, there are represented three cotyledonary 
strands, c. 1, c. 2, and c. 3, and one plumular strand,/. This latter consists 
almost entirely of phloem, but xylem-elements pass outwards from c. 1 and 
c. 2 and divide into two parts, one of which accompanies and completes the 
bundle p (Diagram 7, Fig. 13), and the other for the moment is isolated, 
then it is joined by a strand of phloem from c. 2, so that there is formed, 
between c. 1 and c. 2, a collateral bundle showing reversed orientation, which 
quickly effects a junction with c. 1. 
Directly after these bicollateral bundles have been organized there is 
a junction of three bundles to form one situated in the intercotyledonary 
plane : thus c. 16, c. 7, and c. 8 join to form c. 17, and c. 13, after its division 
into two, combines with c. 12 to form c. 18 (Diagram 7, Figs. 4, 5, and 6). 
Thus there are formed two large bicollateral bundles with xylem on both 
sides of the phloem, and in them the extension outwards of the normally 
