164 



The Araucariece, Recent and Extinct. 



of the young root of A. BidwiUii was found to branch into two steles of equal 

 size. 



V and VI. Boot and Stem Anatomy. — A general account is given of the 

 characteristic features of the anatomy of both genera based partly on the 

 work of others and in part on our own investigations. 



VII and VIII. Leaves and Leaf-traces. — Several types of leaves are 

 described with special reference to the relative abundance of centripetal and 

 centrifugal xylem in the veins. The relation of the leaf-traces to the stem- 

 wood is discussed at length, and some account is given of the behaviour of 

 the traces during the growth in thickness of the stem. 



IX. Reproductive Shoots. — This section includes an account of the male and 

 female flowers of Agathis and Araucaria, special attention being paid to the 

 course of the vascular bundles in the sporophylls. We are led to the con- 

 clusion that the cone-scales of the female flowers are simple structures 

 homologous with foliage leaves. A description is given of the ovules and 

 embryos of Araucaria imhricata. 



X. Fossil Araucariece. — The records of fossil representatives of the two sur- 

 viving genera are critically examined, and evidence is adduced in support of 

 our contention that the Araucariece constitute one of the oldest sections of 

 the Coniferales. 



XL Phylogenctic Considerations and Conclusion. — A comparison is made 

 between the Araucariece and Lycopodiales ; arguments are advanced in favour 

 of the view that this group of Gymnosperms, unlike the Cycadales, was pro- 

 bably derived from Lycopodiaceous ancestors. We draw attention to the 

 various characters in which the Araucariece differ from other members of the 

 Coniferales, and suggest the advisability of giving more definite expression 

 to their somewhat isolated position by substituting the designation 

 Araucariales for Araucariece. 



Our contention is that the general consent which has deservedly been given 

 to the view that the Cycadales and Filicales are intimately connected by 

 descent, may have the effect of inducing an attitude too prone to over-estimate 

 the value of the arguments advanced in support of an extension of the idea of 

 a filicinean ancestry to other sections of the Gymnosperms. 



