Worsdell . — The Structure and Origin of the Cycadaceae . 137 
Matte found in this region of the stem of a seedling of Encephalartos 
Bar ter i (as viewed in transverse section), instead of the usual continuous 
cylinder of endarch structure, three practically independent , distinct steles , 
each of very sinuous, irregular contour, and not forming a definite cylinder 
(Fig. 1). This is, to my mind, the most important recent discovery in the 
structure of Cycads. Its significance, for my point of view, is immense. 
For this structure is clearly exactly comparable to that of such a type as 
Medullosa anglica , Scott (Fig. 1 a), above described 1 . It is an ancestral 
character, found here, and here only, in the very region we should most 
expect it, and soon lost as, passing upwards, the steles unroll and gradually 
Fig. 2. Stangeria paradoxa : transverse section of lower (not lowest) region of vascular ring 
of peduncle of cone showing irregular orientation of the bundles (diagrammatic and reversed) 
(after Scott). 
constitute the typical cylinder. This is the only instance of the kind 
hitherto observed in the vegetative stem. 
In the structure of the peduncle of Stangeria , however, there is, in my 
opinion, further evidence available that the central cylinder is in reality 
composed of the one-sided remnants of a number of steles. In the lowest 
part of the peduncle there is nothing exceptional to be seen ; but some- 
what higher up, i.e. sufficiently so for the organ to exhibit its distinctive 
character, uninfluenced by the region of its origin lower down, the com- 
ponent bundles of the cylinder become orientated in a very irregular way : 
some lying back to back, with their long axes directed towards the centre 
of the organ, and at the same time more or less incurved at the ends, while 
others are horse-shoe-shaped ; and one is completely concentric , with 
central protoxylem (Fig. 2). This peculiar structure can be readily ex- 
plained if we suppose that the whole cylinder has been derived by 
1 Dr. Matte informs me that there was no trace of any injury to the tissues in this region of the 
seedling-axis. He observed this structure in a single individual only ; other seedlings did not 
possess it. He has since kindly enabled me to examine the sections for myself. 
