335 
Actinostrobus pyramidalis, Miq . 
that all four nuclei (two male cells and two sterile nuclei) were embedded 
in a common mass of cytoplasm, which did not, therefore, become organized 
into definite cells around the two male nuclei only, but remained diffuse in 
the tube. Since all four nuclei were exposed to the same nutritive con- 
ditions, they all developed to an approximately equal size. The lowest 
nucleus, being in contact with the larger bulk of the cytoplasm, has, 
however, grown a little larger than the rest. It is probable, as noted above, 
that the archegonia associated with this tube were slightly abnormal, though 
not markedly so. 
5. Fertilization and Embryogeny. 
Since the details of proembryo formation were not satisfactorily 
elucidated in either Widdringtonia or Callitris , attention has been some- 
what concentrated on this phase of the life-history in Actinostrobus , and all 
’ the points of chief importance have been satisfactorily made out. 
Certain points were definitely ascertained in regard to the development 
of the proembryo of Widdringtonia , which Coulter and Chamberlain ( 5 ) 
have incorrectly amplified. They say : ‘ Saxton states, furthermore, that 
walls appear in the proembryo of Widdringtonia before the eight-nucleate 
stage, which probably means that they appear during the transition from 
the four-nucleate to the eight-nucleate stage, as in most Pinaceae.’ In the 
paper (20) to which reference is there made, a figure was given, described in 
the text, of a proembryo containing five resting nuclei, between which walls 
had already been laid down. If Coulter and Chamberlain wish to ignore the 
conclusions to which investigated facts have led the investigators, they 
should at least be very careful not to misstate the facts. 
Assuming, as is at least reasonably probable, that Callitris and 
Widdringtonia agree with one another in the main points of their pro- 
embryo development, the following are the facts known in regard to 
fertilization and embryogeny in those genera: (1) The male and female 
nuclei at the time of fertilization are equal in size and similar in structure. 
(2) The first division of the fusion nucleus results in the formation of two 
free nuclei. (3) Walls are formed while there are still less than eight 
nuclei in the proembryo. (4) Subsequent divisions result in a mature pro- 
embryo of about a dozen cells or less, which completely fills the archegonium. 
(5) In Callitris at least, perhaps not in Widdringtonia , groups of two or 
three cells probably separate from one another, and in each group the 
lowest cell (in regard to the apex of the prothallus, not to the apex of 
the archegonium) gives rise to the embryo, and the cell next above it to the 
suspensor. 
There is now presented a fairly complete account of the corresponding 
phases in Actinostrobus. 
Fertilization has been seen in a considerable number of preparations, 
A a 2 
