6o 
Eric Drabble. 
A section at 4, shows a similar arrangement of the bundles, but 
here there is a more extensive development of xylem, which is 
typically endarch in its arrangement. The phloem groups are 
frequently double, that is, two phloem groups may be found in 
conjunction with a single xylem bundle, and further fusion of bundles 
is seen to be going on. The fibrous sheath is somewhat less dense 
than at 5, and is relegated more particularly to the outer side of 
the bundle. The ground parenchyma is richly intermixed with 
lignified stone-cells—towards the periphery of the section these 
elements occur almost to the exclusion of all else. Amongst these 
are many mucilage cells containing bundles of raphides. 
At 3, the number of bundles is further reduced to thirty-three, 
and the xylem is still very distinctly endarch. Some of the bundles 
show the double phloem groups, and the ground tissue is still 
provided with stone-cells, though somewhat less richly. Orientation 
of the bundles is frequently inverse, and fusions of bundles by 
their xylem portions are found, so producing a xylem-mass bounded 
both externally and internally by a phloem-group. The bundles 
are often roughly arranged in rings, the protoxylem of each bundle 
being orientated with reference, not to the centre of the cotyledon 
stalk, but to the centre of its own ring. 
At 2, the number of bundles is reduced to sixteen. Many show 
double phloem-groups, and there is still indication of the grouping 
of bundles in sets round their own centre. The ground tissue is 
now almost entirely parenchymatous, and large irregular air spaces, 
similar to those described in the mature roots are present. 
At 1, the number of bundles is reduced to nine. The xylem is 
fairly well developed, and the phloem is very abundant and 
arranged in a horseshoe-like form round the outside of each xylem - 
group. Some indication of the grouping of the bundles described 
above is still apparent, the protoxylems of all the bundles in any 
group converging towards one another as indicated in (Fig. 8, ii.) 
The ground parenchyma here encloses very large and extensive 
air-spaces. Surrounding each bundle is a layer of cells, some 3—4 
elements in thickness with very thin and highly refractive walls, 
looking, under the high power of the microscope, as though they 
were cuticularized, but not responding to the endodermic test 
(iodine and strong sulphuric acid). 
At 6, the arrangement of the nine, bundles is almost identical; 
the grouping into three sets is however still better shown, and 
large and extensive air-spaces are present in the ground parenchyma. 
The sheath of small cells surrounding the bundle is here much as 
