CHAPTER XLVIL 



CALLITRIXEAE. 



IT has already been pointed out that there is good reason for 

 treating the three existing genera Callitris, Widdringtonia, and 

 Actinoslrobus as members of a distinct family. The genus Tetra- 

 clinis, as Saxton 1 has shown, while agreeing with the Callitrineae 

 in certain features, exhibits a closer resemblance in its gametophyte 

 to the Cupressineae and is regarded as a type connecting the two 

 families Cupressineae and Callitrineae. So far as external characters 

 are concerned, and these are the features from which the palaeo- 

 botanist is compelled to draw such conclusions as he can, Tetraclinis 

 falls into line with the Callitrineae. The discontinuous distribution 

 of the recent species of these four genera suggests antiquity and a 

 former more extended range. Palaeobotanical literature contains 

 numerous records of Widdringtonia, Callitris, Frenela or Freneliles 

 based in many cases on sterile shoots and sometimes on cones and 

 seeds more or less closely resembling those of recent forms. The 

 generic name Frenela has now been discarded in favour of Callitris : 

 it was proposed by Miquel in 1826 to avoid confusion between 

 Callitris and Calythrix, the latter being the name of a Myrtaceous 

 genus. An inspection of the published figures of supposed fossil 

 representatives of the Callitrineae shows that the name Widdring- 

 tonia or Widdringtonites has sometimes been applied to fertile 

 shoots with cones differing in the number of the valves from those 

 of recent species and more closely resembling the cones of Callitris, 

 Tetraclinis, or Actinostrobus. Moreover the number of valves in 

 recent cones, though usually constant, is not invariably the same 

 and in imperfectly preserved specimens it is often difficult to 

 differentiate satisfactorily between the four genera. In the case of 

 many sterile shoots preserved as impressions it is practically im- 

 possible to distinguish clearly between those of the Callitrineae and 



1 Saxton (13 2 ); (13 3 ). 



