The Seedling Structure of Araucaria Bidwillii. 
BY 
F. J. F. SHAW, B.Sc. (Lond.), A.R.C.S. 
With Plate XXI and six Diagrams in the Text. 
T HE seedling structure of Gymnosperms has till lately been somewhat 
neglected. In a recent paper, Hill ( 2 ) has described the transition 
phenomena in some species, chiefly Cupressineae and Taxaceae, and at an 
earlier date Seward ( 4 ) has given a partial account of the seedling anatomy 
of two species of Araucariae, the two species dealt with being A. imbricata 
and A. Bidwillii. The present paper is concerned only with Araucaria 
Bidwillii , which was not treated in detail by Seward and Ford. In view of 
the uniformity found to exist in seedling Gymnosperms, so far as at present 
investigated, the wide range of variation in the number of cotyledonary 
bundles and in the structure of the root lends considerable interest to this 
species. 
The specimens were about 1 6 cm. long and i*5 cm. broad at the 
widest part of the hypocotyl. In normal cases a seedling consists of 
a swollen or tuberous hypocotyl passing gradually into a thin root (PI. XXI, 
Fig. i) ; none of the specimens showed cotyledons. The whole of the swollen 
portion, from the point at which the cotyledonary tube joins the axis, to 
a level at which the main axis runs on without any essential change in 
diameter, is considered to be the hypocotyl. In Diagram IV, Fig. 13, 
Sections 3 to 8, corresponding to the Figures of same number in Diagrams 
I and II, are in the hypocotyl. The plumular shoot at the apex of the 
seedling is enclosed in a cotyledonary tube formed from the persistent fused 
bases of the cotyledons, the whole external surface is covered with cork. 
Transition Phenomena. 
For the elucidation of the course of the vascular bundles, series of trans- 
verse sections were cut by hand from the apex to the base of numerous 
seedlings. Longitudinal sections were taken from certain portions to check 
the results. 
At the apex of the seedling the plumular bundles {pi. b .) form a ring 
which runs downwards as far as the point at which the cotyledonary tube joins 
Annals of Botany, Vol. XXIII. No. XC. April, 1909.] 
