112 MR. W. C. WORSDELL ON THE 
In a plant of about the same age as the preceding, but possessing a much more 
swollen stem, which was also forwarded to me by Mr. Groves, no incipient stages of the 
normal extrafascicular tissues were anywhere observed. But a phenomenon of no 
morphological, although of considerable physiological, interest is present in the form of 
great numbers of concentrie strands of very weakly-developed vascular tissue scattered 
throughout the cortex. They were of very varying sizes and shapes, some being quite small 
and cireular, others large and tangentially extended in the form of more or less regular 
ellipses. In most cases the phloem of the strand is internal to the xylem, and the 
whole encloses a pith which is always more or less depleted of its starch, exhibiting thus 
a striking contrast to the ground-tissue of the stem between the strands which is replete 
with that substance: it is this peculiarity which enables the position of these strands 
to be everywhere recognized, even with the naked eye, on a transversely-cut surface of 
the stem. 
This peculiar anomalous thickening has been described by Weiss* in the stem or 
root, as the case may be, of a great number of plants; as also by Schmitz t, L. Koch f, 
and Vóchting $. A satisfactory explanation of the phenomenon is afforded by the 
first-named author, who says: ** In all those plants which grow very rapidly in thickness, 
and form an unusually large amount of reserve foodstuffs, a rapid path of transportation 
is necessary. As the parenchyma transports the substances by means of diffusion and 
the phloem by open pores, the secondary medullary and xylem-, phloem-, or fibro-vascular 
strands are of high importance for these plants.” In Bowenia, as described above, 
these secondary strands occur in the cortex. 
Macrozamta Denisonin, F. Muell, 
A plant having a stem-diameter of about one inch, obtained a few years ago from 
Mr. William Bull, of Chelsea, exhibits the following structure. 
At the base of the insertion of the leaves on the stem is a wide central cylinder fairly 
regular in contour except in those places where a leaf-trace bundle joins it. The 
cylinder varies much in the development of its different parts ; on one side its segments 
are extremely small and reduced to tiny bundles isolated from each other by broad 
medullary rays. The protoxylem is quite deranged and obliterated, and small 
transfusion-like tracheides are seen scattered in the parenchyma to the inside of the 
wood. 
In the cortex and pith mucilage-canals are fairly numerous, but do not appear to form 
such a network as in M. Fraseri, Miq.; they mostly assume a vertical course. 
Medullary bundles are entirely absent. This is extremely important, as exhibiting a 
marked contrast in this respect to M. Fraseri, Miq. 
The leaf-trace bundles during their tangential course have the same development of 
spirally- and reticulately-thickened tracheides as in M. Fraseri, Miq. Where they 
* J. E. Weiss: “ Anatomie und Physiologie fleischig verdickter Wurzeln," Flora, 1880. 
t Schmitz: Sitzungsber. der naturforsch, Gesellsch. zu Halle, 1874. 
t L. Koch: Untersuchungen über die Entwickelungsgeschichte der Crassulaceen. Heidelberg, 1879, 
$ H. Vóchting: Hanstein's Botanische Abhandlungen, iii. 1875, Heft 1. 
