158 



rnOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



have served the purpose of a rhizoma*. The best example that I 

 have seen of the rhizoma of a Cahimitc is that figured in Plate IX. 

 (fig. 21), from a specimen presented by me to the Geological Society 

 many years ago. 



With regard to Calamofhiidron the difficulties are greater, and 

 have been vrell stated by Trot. Williamson in a recent paper in the 

 * Memoirs of the Literary and riiilosphical Society of Manchester't, 

 in which he describes under tlie (generic name Galftmopitiis a peculiar 

 stem, which, while he identifies it in its general cliaracters with 

 Calmniten, he justly regards as being in internal structure distinct 

 from the Cahnnodcndra described by Cotta and Binney. 



The characters of Calamodemlroa as distinguished from ordinary 

 Calamltes may be summed up as follows: — 



{(() The part usually preserved is the internal axis, corresponding 

 to a Sternheryia. It presents ribs similar to those of Cahimites, but 

 more angidar, and almost always having traces of woody fibres capa- 

 ble of showing the structure on some part of their surface. 1 have 

 not seen on these casts any distinct traces of scars or areolcs. These 

 casta of the pith of Cahnnodeadron constitute the greater part, if not 

 the whole of the specimens referred to C. (qyproxlmatus. 



(h) More complete specimens are ii vested witli woody matter, 

 arranged in wedges, and consisting of elongated cells and porous, 

 discigerous, or pseudo-scalariform tissue. My specimens do not 

 show distinctly the arrangement of these; but this has been well 

 described by other observers. Williamson describes medullary rays 

 in the woody bundles in addition to the large cellular tracts inter- 

 vening between them. 



(c) The actual external surface of Cidamodcndron is not certainly 

 known ; but I have been disposed to regard as of this kind those 

 nbbed stems, found in the coal-formation, which have swollen nodes 

 as if caused by the emission of whorls of small branches. I have 

 specimens of these in my collcrtion, which I have hesitated to name 

 or describe untd they could i>e better understood. Prof. Williamson s 

 clescription of C(damopi(m now inclines me to 8upi)0se that they be- 

 long to that genus or to allied forms. 



With regard to the aifinities of the Calamodendra, the structure of 

 the stem raises them above tlie Calamites and modern Emiiseta, and 

 .1 istihcs the conicoture of Brongniart that they may have been gymno- 

 tC" '"^"ni«o"' Carruthers, and Jiinnev, however, attribute to 

 frl,«''^'^ >''?'"''' fr^ictification. In this case they may, as the 

 m^l If 1 ; ^' f ««"«^t'tinj.^ link between Acrogens and Gymno- 

 throw an n^T ^}^^^«"l"^'nt investigations eon finn this view, it will 

 C^,lIJl onT"'^ YK'"" '^'' ^''''^'^' ^ffi"ities of Sl<,dlaria. 

 di "ncth orv J '"' ^'"^^' ^^^ r^mdodendron on the other, arc 

 tr3iStt™w '^'^ ""'' ^^^^^"^ to, or included in, the mo- 

 seel tTtn?n^^'"''^T^ ^"^ Lycopodiacea). But Calanwdendron 



%X,t " d iHr'^"^ ^''^ ^^t^'^'^" ^^"^-'-•^'^^ -"d the ribbed 

 J ana, and m hke manner LepidopJdoios seems to connect the 



m 



^M' 



* '^"X.1w &'^ ^^"^- '''^''^- «-!■ Soe. vol. 



X. 



I 

 i 



BlHMJ— l 



