34 ° Saxton. — Contributions to the Life-history of 
as to its value. The present conclusions, based largely on the study of 
Actinostrobus , supplemented by published work on other Conifers with 
lateral archegonia, are as follows: (i) The occurrence of prothalli with 
lateral archegonia, in Conifers, is regarded as a ‘ mutation ’ from the usual 
type of prothallus. ( 2 ) The production of a prothallus with lateral arche- 
gonia probably occurred at least twice in the phylogeny of the group : (a) 
When the Araucarians were differentiated from the Abietineae, which may 
be regarded as having taken place quite early in the history of Conifers, 
soon after differentiation from the Cordaitales. In the Abietineae the 
somewhat widely separated archegonia of the Cordaitales, as figured in 
Cycadinocarpus (Coulter and Chamberlain after Renault (5)), approximated 
more closely, while in the Araucarians they separated more widely. In 
preparations of Araucaria Cookei and A. excelsa the writer has found the 
archegonia to lie, with their apices pointing obliquely outwards, very 
slightly below the rather flattened apex of the prothallus. Each archego- 
nium has its own layer of well-defined jacket cells, and a rather large 
number of neck cells, which lie at the bottom of a canal very similar to that 
leading to each archegonium in Pinus. It is stated (Seward and Ford (23)), 
that the archegonia may be deep-seated in some cases, but more work 
is needed on the genus before such a statement can be definitely accepted ; 
it is not even clear whether 5 deep-seated ’ in this connexion may not 
mean, merely, sunken at the base of a canal, as in Pimis. (b) When 
the Cupressineae, Callitrineae, and Sequoiineae materialized : doubtless 
a later event than the Araucarian differentiation. The close resem- 
blance, in many respects besides the lateral archegonia, between Sequoia 
and the Callitrineae has already been emphasized, and the conclusion 
seems justified that the two tribes were derived from a common ancestry 
with lateral archegonia, while the Cupressineae developed and retained 
the apical group with a common jacket layer. Where any trace of 
a jacket layer does occur in Callitrineae, it also surrounds a group of 
archegonia as a rule, and not individual archegonia. More often specialized 
jacket cells do not become differentiated at all. 
As regards other relationships, it has been suggested before that of 
all Conifers the Callitrineae come nearest to the Gnetales. The formation 
of the embryo and suspensor from a single proembryonal cell is by no 
means dissimilar to what occurs in Ephedra (Land (13)) and Welwitschia 
(Pearson (IB)), though the formation of a cleavage plane instead of a cell- 
plate is admittedly an important difference. The first three series of 
divisions in the embryo are also identical with those in W elwitschia 
(Pearson (18)). Coulter (4), although regarding any attempt to select the 
tribe of Conifers most nearly related to the Gnetales as ‘ peculiarly un- 
profitable nevertheless implies on a later page that his own selection is 
the Cupressineae. Doubtless he is quite justified in saying that any such 
