The Classification of Conifers. 
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which is common to Juniperus , Thuja, Lihocedrus, Taxodium, 
Cryptomeria, Cunninghamia, Tetraclinis, and probably other genera. 
(V) In Podocarpus and its allies the records are very meagre, 
but, such as they are, suggest a type where wall formation occurs 
later than the eight-nucleate stage; where three tiers are normally 
found in the completed pro-embryo; and where a much larger 
number of cells is found in the two upper tiers than in the embryo 
forming tier, which consists usually of only a single binucleate cell. 
(VI) In Torreya and Taxus the pro-embryo nearly or entirely 
(Torreya) fills the archegonium, in contrast to the previous types 
(except type I) though the number of free nuclear divisions differs 
widely, walls being formed in the four-nucleate stage in Torreya, but 
not till the 16-32-nucleate stage in Taxus. As in type V, the embryo 
tier consists of only a single cell, but this is uninucleate, not 
binucleate; as far as our knowledge extends this type does not 
differ in any other important respect from type V but is more variable. 
(VII) Cephalotaxus differs from type VI in forming four regions 
of cells, of which the upper three correspond to those of types IV to 
VI, while the terminal tier forms a penetrating and protective cap 
similar to that met with in type I; a somewhat similar phenomenon 
also appears in a species of Podocarpus. 
(VIII) The pro-embryo of Sequoia differs markedly from that 
of all other Conifers; there is no free nuclear stage, a wall being 
formed at the first sporophytic mitosis; the mature pro-embryo 
completely fills the archegonium, and consists of a row of five large 
cells, of which the basal forms the embryo, and that next above it 
the suspensor. 
(IX) There is one other type in which the pro-embryo 
completely fills the archegonium, and which also agrees with Torreya 
(type VI) in the fact that walls are formed at the four-nucleate stage. 
After some further divisions groups of two or three cells separate out, 
and in each group the lowest cell forms the embryo and that next above 
it the suspensor. In this case, as in type VIII, the first two division 
walls in the embryo initial are vertical. This type is characteristic 
of Actinostrohus, and of Callitris as far as is known, while Widdring- 
tonia differs from the other two genera in minor points, but agrees 
sufficiently to be included in the same type. 
In the mature embryo the number of cotyledons may be a 
character of some value, but as it varies considerably within a single 
species it does not appear to be particularly reliable, and will not 
be further considered, 
