64 
Sinnott. — The Morphology of the 
the other New Zealand species of the genus. The degree of strobilar 
development may be extremely variable and is an unreliable criterion 
in determining affinities. 
The gradual transition between fertile bracts and vegetative leaves in 
Saxegothea and Microcachrys has been compared with similar conditions in 
Araucaria , but since the same phenomenon occurs in Cunning kamia , 
Cryptomeria , and to a certain extent in other Conifers, it loses its signifi- 
cance. 
The fact that the three genera in question which have well-developed 
cones consist of very few species and are limited in distribution has been 
emphasized by Stiles as an instance of the general principle that such 
restricted types are primitive. Dominance and widespread distribution in 
a group of plants are considered prima facie evidence for its recent origin, 
since the possession of more perfect adaptations gives it superiority over 
less favoured and therefore moribund ancestors. This argument is open to 
considerable criticism , for there is good reason to believe that many groups 
dominant to-day, such as the genus Pinus, are comparatively primitive. 
Unspecialized and plastic organisms, * generalized types,’ are more easily 
adapted to changing conditions, and therefore are often more widely dis- 
tributed than those which are more ‘ advanced ’ and which through their 
higher degree of specialization and complexity are confined to a limited 
environment. 
The occurrence in the pollen-grains of both Araucarineae and Podo- 
carpineae of two primary prothaliial cells which later undergo repeated 
division has also been cited as evidence of the affinity of these two families. 
This resemblance in the male gametophyte appears indeed most easily 
traceable to a common ancestry but to one which must have been 
abietineous in affinity, for the occurrence in Ginkgo and the Abietineae 
of pollen with but two prothaliial cells makes it extremely probable that 
this is the primitive condition for ail the Coniferales, and that the subse- 
quent increase in prothaliial tissue which takes place in the Podocarpineae 
and Araucarineae is a comparatively recent development and not the 
persistence of a primitive structure. 
The entire absence of wings in the pollen of Saxegothea (8) and their 
somewhat irregular development in Microcachrys have led Professor 
Thomson (16) and others to believe that the winged condition in the Podo- 
carpineae has arisen entirely independently from that in the Abietineae, 
and that the early stages in its development are represented in Microcachrys, 
where three, four, five, or six wings may be formed. The occurrence of 
both winged and wingless pollen in Tsuga , and the entire absence of wings 
in Larix and Pseudotsuga alone among the Abietineae, however, are almost 
certainly the results of reduction and loss, for these genera are surely 
not the most primitive members of their family. A similar explanation 
