NOTES ON THE ANATOMY OF WIDDRINGTONIA 

 AND CALLITRIS. 



By W. T. Saxton, M.A., F.L.S. 



Introduction. 



It has long been a disputed point whether certain South 

 African Conifers should be included in the Australian genus 

 Callitris or should constitute a separate genus IViddringtoma. 

 Tne investigation here reported was undertaken partly with 

 the object of finding out whether the anatomy of the two 

 genera w^ould throw any light on this question. As will be 

 seen, the results entirely support the second alternative, but 

 material of only three species has been at present examined, 

 and it would be scarcely safe to generalise without studying 

 other representative species. Incidentally, however, certain 

 peculiarities of structure have been met with, which are unique, 

 so far as the writer is aware, and it is upon these that stress 

 is laid, rather than upon supposed generic differences, which 

 may prove, by further research, to be merely specific. 



Description. 



The anatomy of leaf bases* and stem of Widdringtonia cup- 

 ressoidcs, Callitris verrucosa and Callitris rohiista has been ex- 

 amined, the leaf in transverse sections of young twigs and the 

 stem in transverse, tangential and (in two cases) radial section. 



(z.) Leaf Bases. — Figure i is a sketch of a transverse '-ec- 

 tion of a young twig of Callitris verrucosa, passing through 



Fig. I. 



Fig. 2. 



Fig- 



Transverse section of a young twig of Callitris verrucosa. S = 

 Stomata, X = Xylem, P = Phloem, T = Transfusion tissue. ( x6o.) 

 „ 2. A part of Fig. i more highly magnified. i^ = Hypoderm, A =Tan- 

 nin-sacs, .F = Fibres. Other lettering as in Fig. i. ( x 145.) 



the bases of one whorl of leaves. This shows the position of 

 the vascular bundles, transfusion tissue and stomata. 



* Doubtless the free portion of the leaf (a very small proportion is free) 

 would show a similar structure to the base, but without using embedded 

 material it is difficult to obtain sections. 



