EMBRYO DEVELOPMENT AND POLYEMBRYONY 
in the axil of a bract has doubtless also the morphological equivalent of 
the spur shoot. If the phylloclad, which occupies the same position on 
the stem, could be looked upon as the morphological equivalent of this 
dwarf branch, we should have the dimorphic branches represented in a 
Fig. 89, Diagram representing the affinities of the Coniferales as suggested by 
embryogeny. A, probable range of distribution of apical cell in early embryo; CLp, prob- 
able range of cleavage polyembryony ; Emb.cap, range of distribution of embryo cap; Cx, 
distribution of archegonial complex; R, rosette cells present; R-em, rosette cells that usually 
give rise to rosette embryos; R-{em), rosette cells and rosette embryos occasional only; 
Sp.s, range of distribution of spur shoot. Position of forms marked with asterisk (*) is 
doubtful. 
member of the Podocarpineae. Jeffrey (20) looks upon the spur shoot as 
a primitive feature, and it would appear at least that this dwarf branch is 
a character present in the most primitive representatives of more than one 
line of evolution. 
Unfortunately the embryogeny of a large number of conifers is not 
known, and many forms that have been studied have been described in 
such a way that we are uncertain of the features with which we are most 
concerned in the present discussion. Enough has been described to indicate 
that with some such organization of the facts as here presented, embryogeny 
must occupy a much more important place in the study of comparative 
morphology than has generally been conceded. 
The origin of cleavage polyembryony, a very interesting question, has 
not been shown in any living conifer thus far described. A theory to account 
for the possible origin of this condition has been formulated and is to be 
published at another time. 
