226 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
Genus Sigillaria. 
Hoots stigmaroid. 
Trunk Sternbergia pith. Double woody cylinder pseudo- scalariform within and disci- 
gerous without, with medullary rays and oblique pseudo-scalariform leaf-bundles. 
Inner bark thick, cellular, with many bundles of prosenchymatous tissue. Outer 
bark dense, cellular*. 
Leaf -bases hexagonal or elongated, or confluent on a vertical ridge, placed in vertical 
rows, except in young branches. 
Leaf -scars hexagonal or shield-shaped, with three vascular scars ; the two outer 
largest. 
Fruit-scars in transverse rows or bands, each with a central vascular scar. 
Fruit Trigonocarpon, borne in racemes attached to the fruit-scars. 
If Dr. Dawson is correct in making this last statement in reference to Trigonocarpon , 
all doubt as to the Gymnospermous character of Sigillaria would be at an end, because 
we cannot possibly conceive of that seed belonging to any Cryptogamic plant. But I 
have yet seen no evidence whatever, either in his memoirs or in those of Professor 
Newberry, who entertains the same opinions as Dr. Dawson does, that any such rela- 
tionship exists. Under these circumstances, in the subsequent pages I must include 
Trigonocarpon amongst the Gymnospermous plants, but must exclude the Sigillarice , 
and still regard the latter as Lepidodendroid Cryptogams. 
In my original memoir on the Sternbergice , published in the ‘ Transactions of the 
Literary and Philosophical Society of Manchester ’ in 1852, I described a small branch 
of a JDadoxylon from Coalbrookdale, for which I was, many years ago, indebted to Pro- 
fessor Prestwich. This specimen continues to be incomparably the most perfect example 
of its class yet discovered ; hence I have felt it necessary carefully to restudy my sections 
of it, and now proceed to give the results of this renewed examination. 
The specimen has been a young branch about half an inch in diameter. In this 
respect it corresponds with many that we find in the Oldham deposits ; but the interest 
of the specimen lies in the exquisite manner in which all the tissues are preserved. 
The medulla (figs. 33, a, & 35, a) has a diameter of about ‘3, and consists of a regular, 
but rather thick- walled, parenchyma, the cells of which are about ‘0025. In the vertical 
section (fig. 35) these cells are seen to be somewhat depressed vertically, their horizontal 
diameter being greater than their vertical one. They also exhibit a tendency to arrange 
themselves in vertical lines. This medulla is an undivided mass for a thickness of about 
*03, but more internally it separates into innumerable thin laminae, which are very con- 
spicuous in the broken fragments of the specimen, but of which I have found it impos- 
sible to prepare microscopic sections, owing to the extremely friable nature of the fer- 
ruginous matrix occupying the interlaminar spaces. This matrix appears to consist of 
* Since the above description was written, Dr. Dawson bas discovered a Sigillaria with a true Diploxyloid 
axis, corresponding exactly with those which I have already described and with the Anabathra of Witham. 
This discovery would probably lead him to modify some of the above definitions. — June 18, 1877. 
