490 
Stiles.— The Podocarpeae. 
anatomy of the leaves, the remarkable uniformity of structure exhibited by 
the male cones, the constant relationship of a single medianly placed ovule 
to a megasporophyll, the simple character of the latter, and the development 
of prothallial tissue in the male gametophyte, 1 all give evidence of the 
natural relationship of the genera here included in the Podocarpeae. That 
we must look for the nearest approach to the common ancestor of them all 
among the types with the megasporophylls aggregated into cones seems 
obvious. Apart from the fact that the fructifications of Dacrydium and Podo- 
carpus give evidence of their reduction from more perfect cones, 2 it is the 
genera Pherosphaera , Microcachrys , and Saxegothaea which have a very 
limited distribution, and in every group of vascular plants it is as a rule among 
such genera of restricted range that we expect to find the more primitive mem- 
bers of the group. Many species and wide geographical range are the indica- 
tions of a successful genus, and success in the struggle for existence means the 
evolution of characters capable of struggling with modern conditions. For 
this reason, although it is possible, yet it is extremely improbable that a genus 
with a wide range and many species will approach so nearly the primitive 
type of its order as the genera with few species and restricted range, which 
are probably old types making their last stand against newer conditions. 
Again, it is in the structure of these species with female cones that we 
find most indications of primitiveness. The presence of a certain amount 
of centripetal wood in the axes of both the male and female cones of 
Saxegothaea , together with the gradual transition from foliage leaves to 
sporophylls in the case of the female cones, support this view. 
The evidence derived from the development of ovulate structures affords 
fairly conclusive proof that the ovule was originally borne erect in the 
axil of the sporophyll, for it probably arises in this position in all the 
genera, although its position may be altered by later growth (Text-fig. 8). 
It was probably surrounded by a single integument, as it remains presumably 
throughout the whole course of its development in Pherosphaera. 
The male cones are so uniform throughout this order that they afford 
little evidence as to the inter-relationships of the genera. The transverse 
dehiscence of the sporangia of Saxegothaea is probably more primitive than 
the oblique dehiscence in most of the species of Podocarpus. The wood 
of the stem is remarkably uniform throughout the order, but suggests that 
an arrangement of bordered pits in contact is primitive in the order. 
From the account already given of the structure of the leaves of the 
Podocarpeae, 3 it is evident that, with the exception of Nageia , all the leaves 
examined are modifications of one type. The central type is the leaf of 
Saxegothaea or Podocarpus andinus. There is a single vascular bundle with 
well-marked transfusion tissue developed right and left of the xylem, and 
1 Pherosphaera is still unknown in respect of the male gametophyte. 
2 Brooks and Stiles (’ 10 ), p. 314. 8 p. 453. 
