231 
the Sporophylls of the Cycadaceae . 
At a somewhat higher level still, this large strand divides 
up into a row of four, of which the two end-bundles are 
larger, and have their centrifugal xylem developed in such 
a way as to indicate that they are the bundles which are to 
supply the sporangia. Hence, probably on account of the 
lop-sided character of the sporophyll, owing to the extra 
sporangium being present on one side, the vascular system, 
to counterbalance this, is concentrated on this side, the normal 
row of four bundles, instead of being evenly spread over the 
tissues of the sporophyll, as in all other cases, is limited to 
the side on which this extra sporangium occurs. The smaller 
bundle on the other side of the stalk has nothing to do with 
any of the sporangia, but passes up into the lamina. In the 
upper part of the stalk about three smaller ventral bundles 
are seen, one of which is concentric in structure, the others 
irregularly orientated ; tracing these downwards, one of them 
is seen to spring from one of the four bundles of the row, the 
other two, of which the concentric one opens out and becomes 
collateral, end blindly each close up against the rim of a mucilage- 
canal. Higher up, the two end-bundles of the normal row 
are seen to pass off respectively right and left to the sporangia 
(the one supplying the two sporangia much earlier than the 
other). The extra sporangium may be fed by subsequent 
branching of the bundle passing off to the normal sporangium 
on that side ; but the exact course of the bundles to each 
sporangium was not followed. The bundle passing off to 
supply the single sporangium on the other side appears 
to give off a small branch while doing so ; this does not 
happen in the case of the bundle supplying the two sporangia. 
The large bundle found entering the sporangium is almost 
concentric, as in other cases ; on entering the sporangium it 
splits up into a number of parts which radiate out from the 
common centre. 
Fig. 25 a and b represent respectively ventral and lateral- 
views of the sporophyll. 
R 
