564 Saxton .— Contributions to the Life-History of Callitris . 
but, the series not having been very close in either case, some stages are 
missing in the one genus which are present in the other and vice versa. 
TABLE I. 
Organ or Stage. 
Callitrineae. 
Cupressitieae. 
Female cone. 
All cone scales fertile. 
Some cone scales sterile,. 
Ovule. 
Widdringtonia : many mega¬ 
spore mother-cells. 
Callitris : very few megaspore 
mother-cells. 
Very few megaspore mother- 
cells. 
Prothallus. 
Cells eventually bi- and 
multi-nucleate. 
Cells finally uni-nucleate. 
Temporarily bi-nucleate 
in Cryptomeria. 1 
Archegonia. 
Never situated at apex of 
prothallus. 
Number may be under 20 
(Callitris ) or over 100 
( Widdringtonia ). 
Always situated at apex of 
prothallus. Number usually 
few (6-12). Rarely up to 
20 or 30. 
Jacket cells. 
Seldom recognizable. 
Usually well marked. 
Fertilization. 
Male and female nuclei almost 
identical in size. 
Male nucleus smaller than 
female. 
Proembryo. 
Not more than five, possibly 
only two, free nuclei before 
wall-formation. Proembryo 
fills archegonium. 
Eight free nuclei before wall- 
formation. Proembryonever 
fills archegonium. 
Embryo. 
Three or four from single 
proembryo. 
One from each proembryo. 
Of these differences the position of the archegonia and the development 
of the proembryo seem most important, while the bi- and multinucleate 
prothallus cells of Callitrineae also constitute an interesting feature. In 
a recent paper, Coulter ( 5 ), referring to the position of the archegonia 
in Sequoia as reported by Lawson (6), and in Widdringtonia as found 
by the writer ( 13 ), considers the point of only secondary importance on 
account of the fact that it is correlated with the position of the pollen-tube, 
but it seems scarcely reasonable to conclude that because two unusual 
features are correlated with one another, therefore they are of little impor¬ 
tance. Moreover, it has been shown in Callitris , that while ordinarily the 
archegonia are organized in relation to the pollen-tube, yet, in the case of 
the pollen-tube being arrested in its development, the archegonia still 
develop in relation to the position which a normal pollen-tube would have 
occupied. It seems to the writer that this makes it probable that although, 
1 In certain other Conifers, e. g. in Podocarpns (Coker 2 ), multinucleate cells are foimed in the 
prothallus. 
