498 
PROFESSOR W. C. WILLIAMS ON ON THE ORGANIZATION 
exhibit verticils of irregularly disposed protuberances (Plate XXVII. fig. 34, ^) planted 
upon the inferior extremity of each internode. These I have always regarded as indicating 
the exact position of the roots of the Calamites in relation to each node, viz. immediately 
above it. The specimen represented in Plate XXVIII. fig. 35 settles this point. Mr. Binney 
had already published, in his Monograph, a drawing of a fine specimen (page 5), showing a 
large number of the lowermost articulations giving olf roots ; but it afforded no clear evi- 
dence whether those roots were planted above, upon, or below each node. Mr. Wilde’s 
specimen leaves no room for doubt*. Several of its nodes exhibit similar indications to 
that shown in fig. 35, which is a sandstone cast detached from the exterior of the stem, 
preserved by Mr. Wilde; is a smooth surface or cast from which the actual root has 
been separated, hut the latter remains in situ at y/. At its extremity it appears to 
have divided into several slightly diverging branches, or, what is possible, its branched 
portion may have been broken off and the part left split by pressure. Two points are 
clearly indicated by this instructive example : — 1st, the cast of the root is perfectly smooth, 
exhibiting none of the ridges and furrows which are so strongly marked on the inter- 
nodes (Jc) of the parent stem ; 2nd, these ridges and furrows pursue their course right 
across the base of the root, almost entirely undisturbed by its close contact with them. 
These two facts seem to indicate that the root is an adventitious structure, and that 
if it received any vessels from the woody zone they were few in number, and did not 
exist as a cylindrical prolongation of the exogenous woody axis of the stem into the 
root, as would be the case in a recent phanerogamous Exogen. That these roots branch 
at their extremities into the plants known as Pinnularise appears to be established on 
the testimony of so many observers that no grounds exist for doubting the correctness 
of the conclusion, though I have had no opportunity of verifying it. 
A much more difficult question to be determined is the nature and position of the 
aerial branches. When we obtain specimens in which subterranean rhizomes are directly 
prolonged into aerial stems, we find that the large phragmata or cicatricuke, seen in 
Plate XXVII. figs. 31, 32 & 33, give place to others similarly located, but becoming very 
much smaller in size as soon as the stem emerged from the ground. The upper portions 
of the curved lateral aerial stems, appear entirely devoid of all but these smaller cica- 
triculee. Hence we may conclude that in all instances the aerial branches were of small 
diameter. These inferences are sustained by what we know of their minute organiza- 
tion. In my memoir on Calamopitus I gave figures of several transverse sections of these 
branches as seen in tangential sections of the main stem (loc. cit. tab. 3, fig. 6 ; tab. 4, 
fig. 15), whilst in a diagram representing a longitudinal section (tab. 5, fig. 17) I showed 
how these branches spring directly from the innermost part of the woody zone exactly 
at the node ; at the same time I pointed out that, in the sections in question, the dia- 
meter of each branch never exceeded the width of one of the small longitudinal ridges, 
seen on the surface of each Calamite. I have now further evidence of the correctness 
* This position of the roots was long ago shown by Linduey and Hutton in the ‘ Fossil Flora of Great Britain,’ 
Tab. 78 A ; but I have again dwelt upon it because the fact was disputed at the Liverpool Meeting of the British 
Association. 
