35° MORPHOLOGY OF GYMNOSPERMS 



In the present geographic distribution of Taxaceae, the two tribes 

 are in contrast, the podocarps belonging almost exclusively to the 

 southern hemisphere, and the taxads as exclusively to the northern. 

 This associates the former tribe geographically with the araucarians, 

 and the latter with the three other tribes of Pinaceae. 



Among Podocarpineae the genus Podocarpus is the only one that 

 ranges through a hemisphere, and is the only one represented in the 

 northern hemisphere by its extension into Japan. Both Dacrydium 

 and Phyllodadus belong to the Australasian region, but extend north- 

 ward into the East Indies; while Microcachrys and Pherosphaera 

 are restricted to Australasia (chiefly Tasmania), and Saxegoihaea to 

 the southern Andes. The tribe as a whole is distinctly Australasian. 



Among Taxineae the genus Taxus is the only one represented 

 throughout the northern hemisphere, extending southward into tropi- 

 cal Asia and the mountains of Mexico. The other genera are much 

 restricted, Cephalotaxus being found only in Eastern Asia, Acmopyle 

 and Polypodiopsis being restricted to New Caledonia, and Torreya 

 being represented by four scattered species in Florida, California, 

 Japan, and China. The general northern complexion of the group 

 is evident, and the only endemic genus, excluding the two doubtful 

 New Caledonian genera, is Cephalotaxus, all of whose six species 

 occur only in eastern Asia. 



6. Relationship to other gymnosperms 



The opinions that have been expressed in reference to the relation- 

 ships of the Taxaceae are so diverse that it is evident that the family 

 presents a peculiarly difficult combination of resemblances. They 

 have been called the oldest living conifers (133) and the most recent; 

 they have been connected with Ginkgo through Cephalotaxus (124, 

 134), and with Cordaitales on account of the structure of the ovulif- 

 erous shoot of Taxus (134); and the podocarps have been related 

 to the araucarians through Dacrydium and Saxegothaea (150). 



In the absence of any history of the family, only the testimony of 

 reproductive morphology and of vascular anatomy is available. In 

 reviewing this testimony, it seems impossible to regard the family 

 as a natmral one, in the sense that all of its members belong to the 

 same immediate stock. The tracheids of Dacrydium and Saxe!- 



