434 BOTANICAL GAZETTE [December 



This work was done with the advice of Professor R. B. Thomson. 

 I am indebted to him, not only for advice and encouragement, but 

 also for the supply of materials necessary for the work. 



University of Toronto 



LITERATURE CITED 



i. Bailey, I. W., Structure, development, and distribution of so-called rims 

 or bars of Sanio. Bot. Gaz. 68:449-468. 1919. 



2. Don, D., On the structures of the tissues of Cycadeae. Proc. Linn. Soc. 

 London 1 : 53-56. 1840. 



3. Gerry, E., The distribution of the "bars of Sanio" in the Coniferales. 

 Ann. Botany 24:119-123. 191c. 



4. Gothan, W\, Uber die Wandlungen der Hoftupfelung bei den Gymnosper- 

 men imLaufe der Geologischen Epochen und ihre physiologischeBedeutung. 

 Sitzungsb. Gesells. Naturf. Freunde Xo. 2. 1907. 



5. Holden, Ruth, Jurassic coniferous woods from Yorkshire. Ann. Botany 



27:1913- 



6. Jeffrey, E. C, The history, comparative anatomy, and evolution of the 



Araucarioxylon type. Proc. Amer. Acad. 48:531-561. 1912. 



7. Penhallow, D. P., North American Gymnosperms. 1907. 



8. Scott, D. H., Studies in fossil botany. 2d ed. 1909. 



9. Seward, A. C, and Ford, S. O., The Araucarieae, recent and extinct. 

 Phil. Trans. Roy. Soc. London. B. 198:305-411. 1906. 



10. Sifton, H.B., On the occurrence and significance of "bars" or "rims" of 

 Sanio in the Cycads. Bot. Gaz. 60:400-405. 191 5. 



11. Thomson, R. B., On the comparative anatomy and affinities of the Arau- 

 carineae. Phil. Trans. Roy. Soc. London. B. 204:1-50. 1913. 



DESCRIPTION OF PLATES XXXVII, XXXVIII 



PLATE XXXVII 



Fig. i. — Cycas rercoluta: petiole; tangential section of primary wood; 



X225. 



Fig. 2. — Zamia integrifolia: petiole; pitting of primary wood; X445 



wood 



pitting; X445- 



Fig. 4. — Lygenodendron Oldhamium: radial section of secondary w r ood of 

 stem; Xioo. 



Fig. 5. — Cordaites sp.: radial section of secondary wood of stem; X225. 



PLATE XXXVIII 



Fig. 6. — Dioon spinulosum: radial section of secondary wood of stem, 

 showing pit arrangement and bars of Sanio; X225. 



