480 REPORT—1883. 
medullary cavity whilst it was in a plastic state, but which plastic material subse- 
quently became more or less hardened ; its longitudinal grooves being caused by the 
pressure of the inner angles of the numerous longitudinal vascular wedges, and 
the transverse ones, partly by the remains of a cellular nodal diaphragm which 
crossed the fistular medullary cavity, and partly by a centripetal encroachment of 
the vascular zone at each corresponding point. 
My cabinets contain an enormous number of sections of these plants in which 
the minutest details of their organisation are exquisitely preserved. These specimens, 
as already observed, show their structure in every stage of their growth, from the 
minutest twigs to stems more than a foot in diameter. Yet these various examples 
are all, without a solitary exception, constructed upon one common plan. at 
plan is an extremely complicated one ; far too complex to make it in the slightest 
degree probable that it could co-exist in two such very different orders of plants 
as the Hquisetacee and the Gymnosperme ; yet, though very complex, it is, even 
in many of its minuter details, unmistakably the plan upon which the living 
Equisetums are constructed. The resemblances are too clear as well as too 
remarkable, in my mind, to leave room for any doubt on this point. The great 
differences are only such as necessarily resulted from the gradual attainment of the 
arborescent form, so unlike the lowly herbaceous one of their living representatives. 
On the other hand, no living Gymnosperm possesses an organisation that in any 
solitary feature resembles that of the so-called Calamodendra. The two have 
absolutely nothing in common; hence the conclusion that these Calamodendra 
were Gymnospermous plants, is as arbitrary an assumption as could possibly be 
forced upon science; an assumption that no arguments derived from the merely 
external aspects of structureless specimens could ever induce me to accept. 
These Calamites exhibit a remarkable morphological characteristic which 
resents itself to us here for the first time, but which we shall find recurs in other 
Palicesots forms. Some of our French botanical friends group the various 
structures contained in plants into several ‘ Appareils,’? distinguished by the 
functions which those structures have to perform. Amongst others we find the 
* Appareil de soutiens’ embracing those hard woody tissues which may be regarded 
as the supporting skeleton of the pe and the ‘ Appareil conducteur’ which M. 
Van Tieghem describes as composed of two tissues: ‘ Le tissu criblé qui transporte 
essentiellement les matiéres insolubles, et le tissu vasculaire qui conduit l’eau et les 
substances dissoutes,’ Without discussing the scientific limits of this definition, 
it suffices for my present purpose. In nearly all flowering plants these two 
‘ Appareils’ are more or less blended. The supporting wood cells are intermingled, 
in varying degrees, with the sap-conducting vessels, It is so even in the lower 
Gymnosperms, and in the higher ones these wood-cells almost entirely replace the 
vessels. It is altogether otherwise with the fossil Cryptogams. The vascular 
cylinder in the interior of the Calamites, for example, consists wholly of barred 
vessels, a slight modification of the scalariform type so common in all Cryptogams. 
No trace of the ‘ Appareil de soutiens’ is to be found amongst them. ‘The vessels 
are, in the most definite sense, the ‘ Appareils conducteurs’ of these plants ; no such 
absolutely undifferentiated unity of tissue is to be found in the vascular portions of 
any living plants other than Cryptogams. 
But these Calamites, when living, towered high into the air. My friend and 
colleague, Professor Boyd Dawkins, recently assisted me in measuring one, found 
in the roof of the Moorside colliery near Ashton-under-Lyne by Mr. George Wild, 
the very intelligent manager of that and some neighbourme collieries. The 
flattened specimen ran obliquely along the roof, each of its two extremities 
passing out of sight by burying themselves in the opposite sides of the mine. Yet 
the portion which we measured was 380 feet long, its diameter being 6 inches at 
one end, and 4} inches at the other. The mean length of its internodes at its 
broader end was 3 inches, and at its narrower one 1} inches, What the real 
thickness of this specimen was when all its tissues were present, we have no means 
1 See Memoir i. Pl. xxiv. fig. 10, and Pl. xxvi, fig. 24. 
2 Van Tieghem, Zraité de Botanique, p. 679. 
