Saxton.—Contributions to the Life-History of Callitris . 567 
In a former paper ( 13 ) the name Actinostrobeae was used for the four 
genera here named Callitrineae. I had at that time failed to note that 
Masters (8) had already applied the latter name to the same four genera in 
preference to Endlicher’s name which included also Libocedrus. In the 
same paper a comparison was provisionally suggested with the G?ie tales, 
especially with Welwitschia , but further research has shown that the 
resemblances noted are apparent rather than real. Nevertheless it does 
seem likely that of all Conifers Widdringtonia come a trifle nearer the 
Gnetales (at any rate Welwitschia and Gnetuni) than any other genus, at 
any rate in gametophyte characters. Coulter ( 5 ) regards the Gnetales as 
derived from the Cupressineae. 
Summary. 
The microsporophylls are arranged in alternating whorls of three, and 
each bears three microsporangia. 
The six megasporophylls are in two alternating whorls of three, the 
outer somewhat smaller and bearing fewer ovules. 
The young embryo-sac is situated in the apical half of the nucellus. 
The archegonia are never situated at the apex of the prothallus, but 
in a single group of about, or just under, twenty, arranged along the inner 
side of the pollen-tube near its apex. If two pollen-tubes are present, two 
such groups are organized. 
The pollen grain is uninucleate at the time of shedding in C. verrucosa 
and C. robnsta. 
The later development of the male gametophyte is normal. 
The proembryo completely fills the archegonium, but the arrangement 
of the cells is variable. 
More than one embryo is formed from a single proembryo. 
The first two walls in the embryo are longitudinal. 
The mature embryo has two cotyledons. 
The cells of the mature prothallus are all binucleate or multinucleate. 
It is concluded that Widdringtonia and Callitris undoubtedly repre¬ 
sent two distinct genera and must be made the types of a separate tribe of 
Coniferae, the Callitrineae, co-ordinate with Cupressineae. The characters 
of the Callitrineae are in many respects intermediate between those of 
Cupressineae and those of Sequoia. 
Botanical Laboratory, 
South African College, 
Cape Town. 
A T ovember , 1909. 
