Stiles . — The Podocarpeae. 499 
is at least safe to say that there is as yet little evidence of any near con- 
nexion of the Taxeae and Podocarpeae. 
Workers on gametophytic structure have found several points of 
similarity between the Abietineae and Podocarpeae . 1 In the first place, 
prothallial cells are developed in the male gametophytes of each order, but 
whereas these are evanescent structures in the Abietineae, in the Podo- 
carpeae they are generally more numerous and may persist up to the 
time of fertilization. The distribution and arrangement of the archegonia 
is also similar, and a third point of resemblance is found in the reduction of 
the functional male nuclei to one. As regards sporophytic characters, male 
cones and microsporangia are similarly constructed in the two groups, while 
in each order the pollen-grains are winged. This last point appears to 
be another case of parallel evolution, for in the Podocarpeae the wings 
seem to have arisen within the group itself, for the pollen of Saxegothaea 
is wingless, while in Microcachrys the wings are imperfectly developed . 2 
Among the Abietineae also the genus Psendotsiiga has wingless pollen . 3 
As regards the distribution of the archegonia we find a similar arrangement 
in the Taxeae and in Sciadopitysf while the reduction of the functional males 
to one is probably to be correlated with the absence of archegonial com- 
plexes . 5 On the other hand, there are great dissimilarities in the structure 
of the wood of the stem, and in the female fructification. The relative 
phylogenetic value of different characters is always a difficult thing to 
estimate, and personal opinions on such a question will probably always 
vary to some extent. The opinion of most workers is that it is to the 
reproductive structures, rather than vegetative characters, such as wood 
structure, that we should look for indications of relationship. In the case 
under consideration the differences between the simple cone scale of the 
more primitive Podocarpeae bearing a single ovule, and the more compli- 
cated < pieces du cone ’ of the Abietineae each bearing two ovules, indicate 
that the relationship between the two orders cannot be a very near one. 
On the other hand, there are several characters which seem to indicate 
a common ancestry of the two orders, chief among which must be reckoned 
the similarity of the microsporophylls, the distribution of archegonia in the 
female gametophyte, the development of prothallial tissue in the male 
gametophyte, and the inversion of the ovules. In the last two instances the 
facts indicate that the Abietineae have advanced much further from the 
common ancestor than the Podocarpeae, for the prothallial tissue is reduced 
not only in amount but also in the length of time it persists, while the 
inversion of the ovules is much more complete. The position of the ovule 
on an outgrowth of the scale in P odocarpus , and especially the position 
1 Coker (’02), p. 102; Young (’07), p. 194; Burlingame (’08), p. 175. 
2 Thomson (’09 1 ), p. 29. 8 Lawson (’09), p. 163. 
4 Lawson (TO), p. 412. 5 Lawson (’07 2 ), p. 292. 
