INTERIOR OF TRUNKS. 471 
filled the interior of these trunks, it follows that 
they must have been without any transverse dis- 
sepiments, and hollow throughout, at the time 
when the sand, and mud, and fragments of other 
plants, found admission to their interior. The 
bark, which alone remains, and has been con- 
verted into coal, probably surrounded an axis 
composed of soft and perishable pulpy matter, 
like the fleshy interior of the stems of living 
Cacteae ; and the . decay of this soft internal 
trunk, whilst the stems were floating in the 
water, probably made room for the introduction 
of the sand and clay. 
These trunks usually vary from half a foot to 
three feet in diameter. When perfect, the height 
nearly vertical. The interior of those whose inclination exceeded 
45° was filled with an indurated mixture of clay and sand ; the 
lower extremity of several rested on the upper surface of the bed 
of Coal. None had any traces of Roots, nor could any one of 
them have grown in its present place. 
M. Alex. Brongniart has engraved a section at St. Etienne, in 
which many similar stems are seen in an erect position, in sand- 
stone of the Coal formation, and infers from this fact that they 
grew on the spot where they are now found. M. Constant 
Prevost justly objects to this inference, that, had they grown on 
the spot, they would all have been rooted in the same stratum, 
and not have had their bases in different strata. When I visited 
these quarries in 1826, there were other trunks, more numerous 
than the upright ones, inclined in various directions. 
I have seen but one example, viz. that of Balgray quarry, three 
miles N. of Glasgow, of erect stumps of large trees fixed by their 
roots in sand-stone of the coal formation, in which, when soft, 
they appear to have grown, close to one another. See Lond. 
and Edin. Phil. Mag. Dec. 1835, p. 487. 
