Anatomy of the Seedling and Young Plant of 
Macrozamia Fraseri. 
BY 
E. J. HATFIELD. 
With Plate XXII and eight Figures in the Text. 
T HE anatomy of the genus Macrozamia has received attention at 
the hands of several botanists. In 1902 Miss Robertson 1 gave 
a summary of the chief results derived from studies of the genus up 
to that date. 
The anatomy of the species M. Fraseri is of peculiar interest, for it was 
the discovery by Worsdell 2 of secondary and of tertiary ‘ inverted ’ anoma- 
lous rings of xylem in the mature stem which led to the formulation of the 
Medullosean theory of the origin of the Cycads. In view of the importance 
that has been attached to the adult anatomy, Dr. Thomas suggested that an 
investigation of young plants recently obtained by her in Australia seemed 
desirable. 
The examination of germinating seeds revealed a structure quite 
comparable in its main features with that recorded for other seedlings 
of the genus 3 » 4 > 5 j 6 and upon which the generalized account of Cycadean 
seedling anatomy given by Coulter and Chamberlain is founded ; but, 
if transition phenomena be figured in the diagrammatic form given by 
them, the transition in Macrozamia Fraseri corresponds rather to that 
given for Ginkgo , Gnetinn , and Araucaria than to those representing 
the Cycadean genera. In the young plants, while some of the structures 
found in the adult are absent — e. g. pith bundles, ‘ inverted ’ anomalous 
rings, & c. — a hitherto undescribed anomaly is revealed in the epicotyle- 
donary region. This is a gradual tangential extension of the cambium, and 
of the elements to which it gives rise, until a vascular cylinder is developed, 
which resembles in this feature the structure found by Dr. Stopes 7 in the 
1 Robertson : Proceedings of the Cambridge Philosophical Society, vol. xii, Part I. 
2 Worsdell: Ann. Bot., vol. x, 1896. 
3 Dorety : Vascular Anatomy of the Seedling of Microcycas calocoma. Bot. Gazette, vol. xlvii, 
1909. 
4 Dorety : The Seedling of Ceratozaniia. Bot. Gazette, vol. xlvi, 1908. 
5 Thiessen : Anatomy of the Seedling of Dioon edule. Ibid., 1908. 
6 Hill and de Frame : Seedling Structure of Gymnosperms. III. Ann. Bot., vol. xxiii, 1909. 
7 Stopes : Catalogue of the Cretaceous Flora, Part II, p. 314 et seq. 
[Annals of Botany, Vol. XXXV. No. CXL. October, 1921.] 
