Stiles. — The Podocarpeae. 503 
possession of sporophylls with the single sporangium borne medianly in 
relation to the sporophyll . 1 
Now in the Podocarpeae and in the Araucarieae, the relation of ovule 
to megasporophyll is the same. Each sporophyll bears a single sporangium 
medianly on its upper surface. In most cases in the Podocarpeae the 
sporangium in its later stages appears on the surface of the sporophyll and 
not in its axil, and moreover is usually more or less reversed. In every 
case so far investigated, however, the evidence points to the fact that the 
sporangium in the very young strobilus does actually arise in the axil of 
the sporophyll, and in an erect position ; it is only later in its ontogeny that 
it becomes reversed and carried away from the axis. In fact, in the youngest 
stages, which are almost certainly more primitive than the older, the con- 
dition is identical with that in the Lycopodiales. Among the latter the 
genus Spencerites affords an interesting comparison with the Podocarpeae, 
for here the sporangium is borne on the upper side of the sporophyll away 
from the axis, and, moreover, may be regarded as reversed. 
The chief evolutionary tendency in the Podocarpeae, as has already 
been pointed out, is reduction in the number of sporophylls in the female 
strobilus. What are regarded as the more primitive members of the order 
still, however, retain their sporophylls in cones, and so approach more 
nearly the majority of Lycopods than do the more specialized Podo- 
carpeae. 
The microsporophylls also are easily comparable with those of the 
Lycopods. The sporophylls are still aggregated into cones, but whereas in 
the Lycopods there is constantly a single microsporangium in the axil of 
each microsporophyll, in the Podocarpeae there are constantly two borne 
on the under side. This difference is not a very serious one. That septation 
of a single sporangium into more than one has taken place in other cases is 
more than probable. Indeed, the two sporangia forming the synangium of 
Tmesipteris , and the three sporangia in the sporangiophore of P silo turn , are 
considered by some botanists as derived in this way 2 from the single 
sporangium as it exists in the Lycopod, and in Lepidostrobus Brownii and 
in Isoetes we have cases in which this septation by means of sterilization 
of formerly sporogenous tissue has proceeded only partially towards 
completion . 3 Indeed, such a case of incipient septation may be present 
in the genus Lycopodium itself, as in Lycopodimn clavatum . 4 
The shifting of the sporangia to the under side presents little difficulty 
to the view under consideration. Shifting of the position of the sporangia 
in regard to the sporophyll has certainly taken place in other cases. It is 
possible, though indeed not by any means certain, that in the Ferns the 
position of the sori has shifted from a marginal to a superficial one . 5 
1 Bower (’08), p. 326. 2 1. c., p. 427. 3 1. c., pp. 326, 697. 
4 Sykes (’08), p. 50, Text-fig. 7, ix. 5 Bower (’08), p. 663. 
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