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ON THE GENUS KNORRLA, Sternd. 
By W. Carrutuers, F.L.S., F.G.S. 
(Puate XCIII.) 
This genus was established by Sternberg, in the ‘Tentamen Flora 
Primordialis’ (p. xxxvii.), which accompanied the first volume of his 
‘Flora der Vorwelt,’ for two stems which he considered to be dico- 
tyledonous, and to have been clothed with fleshy cylindrical leaves, 
like some succulent plants. The fossils were casts found in beds be- 
longing to the Coal-measures. Stems that are imbedded in sandstone 
have frequently entirely perished, and the cavity remaining having been 
afterwards filled in with amorphous material, there is no indication of 
the fossil except this cast of the original, which shows often in the most 
perfect manner all the external characters of the stem, but without 
any trace of its internal structure. As a consequence, considerable 
uncertainty has always existed as to the true nature of these fossils. 
ey are described as decorticated stems, without any definite mean- 
ing being attached to the term ‘ decorticated.’ 
Professor Williamson has clearly established that some Sternbergias 
are the casts of the medullary axis of Dadoaylon. Endogenites striata of 
Lindley and Hutton is a similar cast of that or an allied coniferous 
genus. The most familiar condition of Calamites, as a fluted and con- 
stricted stem, is in like manner only the cast of the medullary or cel- 
‘lular axis; the thin incrustation of coal which is attached to it when 
it is removed from the rocky matrix, representing the greatly altered 
woody tissue. Knorria also is the cast of the interior of a Lepido- 
dendroid stem, as was at first supposed by Sternberg, though he after- 
wards changed his opinion, and by many subsequent writers as Gceppert, 
Dawson, etc. It has been described by these authors as “ decorti- 
cated.” In the stems mentioned, with the exception of Knorria, the 
“cortex”? means the whole of the woody tissue, as well as the cortex 
properly so-called. In Lepidodendron, however, the wood is a very 
slender cylinder in the centre of the stem, while the casts of Knorria 
have a considerable diameter. A specimen from the Coal-measures, 
near Edinburgh, for which I am indebted to Charles Peach, Fsq., whose 
long-educated eye appreciated its value, exhibits the relation of the cast 
to the complete stem. In the lower part of the specimen, the short 
VOL. Vir. [JULY 1, 1869.] N 
