The Anatomical Characters presented by the 
Peduncle of Cycadaceae. 
BY 
D. H. SCOTT, M.A., Ph.D., F.R.S., 
Honorary Keeper of the Jodrell Laboratory , Royal Gardens , Kew. 
With Plates XX and XXI. 
Introduction. 
HE peculiar structure of the vascular bundles in the 
X leaves of Cycadaceae has been well known to botanists 
since its discovery by Mettenius in i860 1 . The peculiarity 
depends on the position of the spiral tracheae, which are the 
first formed elements (protoxylem) of the wood. In ordinary 
collateral bundles, such as those in the stem of Coniferae, 
and in both stem and leaf of most Angiosperms, the spiral 
elements lie at the extreme inner edge of the wood, remote 
from the phloem. Thus the whole development of the xylem, 
starting from the spiral tracheae, and advancing towards the 
phloem, proceeds in centrifugal order. In the foliar bundles 
of Cycads, on the other hand, the spiral elements are placed 
in the interior of the strand of xylem, but nearer the outer 
1 Mettenius, Beitrage zur Anatomie der Cycadeen ; Abhandl. d. I\. Sach . 
Gesellsch. d. Wissl Bd. vii, p. 567, i860. 
[Annals of Botany, Vol. XI. No. XLIJI. September, 1897.] 
