GENERAL RESULTS— PTEROPSIDA 655 



are relatively primitive Conifers, a point on which I am 

 disposed to agree with Professor Seward, it appears that 

 the more complex type of leaf-structure is the original 

 one for the Order. While the general anatomy of the 

 leaf is thus entirely favourable to Cordaitean affinities, 

 the histology lends no decided support to either view of 

 the affinities. The vascular bundles have no typical 

 centripetal wood, but are accompanied by trans- 

 fusion-tissue, which we may either regard, with Mr. 

 Worsdell and M. Bernard, as representing the centripetal 

 xylem of Cordaiteae, 1 or may compare with the well- 

 developed transfusion-tissue occurring in fossil Lycopods. 

 On any view, the centripetal part of the xylem is a 

 tissue which becomes modified or lost in the higher 

 plants. 2 



Passing on to the organs of reproduction, the male 

 cones of Araucarieae show some points in common 

 with those of Cordaiteae. As we have seen, the 

 stamens of the latter group have been well compared 

 with those of Ginkgo. The stamens of Araucarieae, 

 with their distally attached pollen -sacs, are of the 

 same type as in Ginkgo, but the large number of the 

 sacs brings them nearer to the Cordaitean stamen ; 

 on the other hand they differ absolutely from the 

 sporophylls of the Lycopods, in which the constant 

 relation of one sporangium to one sporophyll is a 



1 It will be remembered that, according to Miss Stopes's observations, 

 transfusion-tissue, as well as centripetal xylem, occurs in the Cordaitean 



leaf (p. 534). 



2 The structure of Araucarian seedlings obviously cannot be used in the 

 comparison with a fossil group. Recent work, however, shows that the 

 anatomy of the seedling in Araucarieae conforms to the same type as that 

 of the Cycadaceae and Ginkgo, while other Coniferae show a modification 

 of the type in the direction of reduction. 



