254 
W. T. Saxton. 
The position of certain genera in this scheme of classification 
is quite uncertain, as has been indicated. Those included under 
the heading of “ probably ” in the families and sub-families are not 
considered likely to show marked divergences in gametophyte and 
pro-embryo characters, when these are more fully known, hut the 
position of those “possibly” included is very uncertain, and the 
genera Fitzroya (including Disehna), Atlirotaxis, Glyptostrobus , 
Taiwania, Acmopyle, Polypodiopsis and Pherosphcera would certainly 
repay a detailed investigation. If, however, the general principles 
used as the basis of such a classification are regarded as valid, it 
cannot be logically urged that some other and more artificial 
grouping of the genera should be preferred, which would enable 
every genus to be at once placed in its final position. On the 
contrary, the uncertainty in regard to the natural position of these 
genera can only be used as an argument for their immediate 
investigation. A more serious disadvantage is that we have an 
extremely limited acquaintance with gametophyte and pro-embryo 
structures amongst fossil Gymnosperms; still, the same argument 
applies, that we cannot discard a natural in favour of an artificial 
classification for the sake of cataloguing fossils, though there has 
been a tendency of late to do something of this kind. 
The families and sub-families here proposed may be defined (in 
regard to gametophyte and pro-embryo characters only) as follows: 
I. Archegonia more or less lateral, not united in groups; apex 
of prothallus truncate; male gametophyte with a considerable 
number of prothallial nuclei; male cells nearly equal; pro-embryo 
forming a considerable number (32 or more) of free nuclei in a 
central mass of cytoplasm, before wall-formation; lowest tier 
of cells forming a penetrating and protective cap; male and 
female nuclei equal (or almost equal) in size at the time of 
fertilization. ....... Araucayiacece. 
II. Archegonia apical, each with its own jacket-layer, not 
united in a complex ; male gametophyte with two or more prothallial 
nuclei, usually persistent; male cells very unequal; pro-embryo 
forming about 16 free nuclei before wall-formation, at base of 
archegonium; usually no cap-cells; single binucleate embryo-cell 
at the tip of the pro-embryo. .... Podoccirpacece. 
III. Archegonia as in II; male gametophyte with two transient 
prothallial cells, or none; male cells (or nuclei) nearly equal; pro¬ 
embryo with eight or more free nuclei at base of archegonium before 
wall-formation, later organising four regular tiers of cells (free 
