Saxton.—Contributions to the Life-History of Callitris. 563 
region, showing the persistently multinucleate cells of the prothallus. This 
character can be clearly seen in the photograph from which Fig. 1, PL XLVI 
is reproduced, but is not likely to be apparent in a half-tone reproduction. 
The mature embryo has invariably been found to possess two cotyle¬ 
dons. The germination is of the same type as in Widdringtonia , but the 
seedling is very much more slender than in that genus. The succession of 
plumular leaves is also the same in the two genera ; that of Callitris is 
shown in Fig. 2, PL XLVI. 
7. Abnormalities . One case has already been mentioned where a super¬ 
numerary nucleus was present in the mature pollen-tube (P'ig. 16), but the 
case shown in Fig. 25 is still more remarkable. Here the dilated tip of the 
pollen tube has put out a slender tube below, suggestive of a haustorial 
function, and in the swollen part are found five nuclei, all practically alike 
in size and structure. In the prothallus, surrounding the enlarged part 
of the tube, are a considerable number of archegonium initials. 
Fig. 3, PL XLVI represents a prothallus which is only abnormal in the 
fact that no pollen-tube has yet penetrated it, and yet cell-division is com¬ 
plete and archegonium initials have appeared. The latter are clearly seen 
to be endogenous in origin. This figure will be referred to again later. 
8. Discussion and Conclusions. As was stated above (p. 557) this dis¬ 
cussion and the conclusions arrived at are based partly on the facts here 
reported, and partly on the corresponding facts in the life-history of 
Widdrmgtonia , as recently described by the writer. 
The main conclusion reached from these studies is that Callitris and 
Widdringtonia must be placed in a tribe apart from those Cupressineae 
which have been fully investigated, and no longer included as a sub-tribe of 
Cupressineae. 
Masters (8) has already separated these two genera together with 
Tetraclinis and Actinostrobus as the sub-tribe Callitrineae, but has included 
them in the tribe Cupressineae. Most other authors (e. g. Rendle ( 12 )) have 
not recognized even the subtribal distinction. 
The writer suggests that the Callitrineae as defined by Masters (loc. cit.) 
should be raised to the rank of a tribe, co-ordinate with the Cupressineae, 
although the inclusion of Tetraclinis and Actinostrobus must be merely 
provisional until their life-histories have been worked out. 
It is hoped that at a future date material of these genera may be avail¬ 
able for investigation in order to ascertain whether or not their life-history 
does conform to that of Callitris and Widdringtonia. 
In Table I, showing the chief differences between the Callitrineae and 
the Cupressineae, it has been assumed that certain points only definitely 
ascertained for one genus will be found to hold good for both. It may be 
pointed out that where this is done (fertilization and post-fertilization stages) 
there is considerable evidence that the two genera will be found to agree, 
