Scott.—The Structure of Mesoxytou multirame. 441 
any distinction between the trace-bundles and the median strand ; all three 
have split up and rearranged their parts so as to form a single whole. The 
structure appears to have become endarch as shown in PL XIII, Fig. no, 
which represents another trace at about the same level. 
In the lowest section, 2343, the trace is less prominent, and some more 
fusion among the various tracheal bands has taken place. 
It will be seen that in the behaviour of the trace-bundles after reaching 
the border of the pith there are considerable differences from M. Lomaxii 
and M. poroxyloides ; in the former species the twin bundles fuse immediately 
bn attaining this position ; the centripetal xylem persists far below the point 
of fusion. In M.poroxyloides fusion also takes place high up—almost as 
soon as the pith is reached. The centripetal xylem of the twin bundles 
fuses in a definite manner (Scott, 1912 , p. 1019), and here also persists for 
a long way down, after fusion has taken place. 
In M . multirame , on the other hand, the twin bundles remain distinct 
for a considerable distance at the edge of the pith. Thus in the case just 
considered, they are reaching the pith in one section, remain quite distinct 
through the next two, and only become united into a common mass in the 
fourth section. There is never in fact a definite fusion , such as we see so 
clearly in the other two species. The two bundles, together with the median 
strand, merely group themselves in one mass. The centripetal xylem has 
already ceased to be distinguishable before this grouping is accomplished. 
The resemblance to M . Sutcliffii is much closer (Maslen, 1911 , p. 396, PI. 
XXXIII, Figs. 3-5); in fact, there appears to be no essential difference in 
the behaviour of the leaf-traces of these two forms. 
One or two other points connected with the course of the bundles may 
be noticed. I have tried to find out whether any regular order is followed 
in the subdivision (or fusion, according to the direction in which we follow 
them) of the bundles of the leaf-trace in the cortex. It will be seen in PI. XI, 
Fig. 3 that each of the two strands of the double trace is dividing unequally, 
the outer segment on either side being about twice as broad as the inner. 
If one follows the trace farther out, one finds, as would be expected, that 
the outer strand on either side divides again; this gives two groups of 
3 bundles each, with a wide space between them. The next stage shows 
less constancy; sometimes the outermost bundle divides once more; some¬ 
times it is the innermost bundle of the 3 that divides ; the two sides of the 
same trace may differ in this respect. In any case there are now 8 bundles, 
which seems to be the regular number entering the base of the leaf. No 
doubt further subdivisions then go on, as in M. Sutcliffii , in which Mr. Maslen 
observed 16 in a petiole (Maslen, 1911 , p. 405). The whole process of 
subdivision of the trace agrees closely with that in M. Sutcliffii , and 
Mr. Maslen’s figures illustrate the essential points sufficiently ( 1 . c., PL 
XXXIV, Figs. 8-10). 
