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the Sporophylls of the Cycadaceae . 
is examined, a similar phenomenon, as might be expected, 
prevails. Here also in the base of the organ, near the point 
of its attachment to the axis of the cone, the bundles are, or 
tend to be, endarch in structure, while in proportion as they 
pass higher up towards the lamina the endarch is gradually 
replaced by the mesarch character, until, in the lamina of the 
organ, the latter predominates. Thus the same general 
structure obtains here as in the foliage-leaf. 
Now the sporophyll has a function to perform which is 
entirely different from that of the foliage-leaf. Whereas the 
function of the latter is to elaborate food-material for the 
supply of the various parts of the plant, to aid in the con- 
duction of water through the stem, and to discharge the 
surplus quantity of this water from its expanded surfaces, 
the function of the sporophyll is to bear the sporangia, and 
to act as channels for the conduction of nutriment of all kinds 
to these latter ; it also, in some cases, takes a small part 
in assimilation. 
Though both foliage-leaf and sporophyll are morpho- 
logically of foliar nature, and possess essentially the same 
structure, their physiological relations are seen to be widely 
divergent It is the special sporangiferous function of the 
sporophyll which has induced those modifications in the 
structure and arrangement of the vascular bundles of this 
organ which are considered worthy to form the subject of 
a separate paper. 
There exists a considerable range of variation as regards 
the external development of the sporophyll in the different 
genera, and sometimes also within the same species between 
the two sexes. They may be either large and leaf-like or 
very much reduced and modified in shape, so as no longer 
to bear much resemblance to ordinary foliar organs. 
In the male sporophyll , as is known, the sporangia are 
thickly arranged in sori on the lower surface of a large 
flattened area situated between the extremely short stalk 
and the terminal, swollen, sterile portion ; the function of the 
latter is to afford protection to the sporangia within ; the apex 
