80 ROYAL SOCIETY OF CANADA 



branches must have been few and thick, unless indeed we suppose that 

 this feature was limited to the main stem, and that small branches of 

 different structure have sprung in whorls from its sides." 



Here rested for many years the study of this interesting species, at 

 least so far as available literature known to me is concerned. In 1900, 

 however. Prof. D. P. Penhallow took up the study of the microscopic 

 structure of various species of North American Dadoxyla and among 

 the rest of D. Ouangondianum, basing his observations on the specimens 

 in the Peter Eedpath Museum at McGill TJniversity,^ which in part had 

 formed the basis of Sir William Dawson's; studies and came to the con- 

 clusion that this species had obscure or obsolete rings of growth. This 

 to me seemed remarkable after the results obtained by so painstaking 

 and acute an observer as Sir William Dawson and I therefore took oc- 

 casion some years ago when passing through Montreal to visit the Eed- 

 path Museum and examine the specimens referred to this species in the 

 cases of fossil plants on exhibition there. I found several examples 

 which showed rings of growth and one (silicified) stem which did not. 

 It may have been from this one that Prof. Penhallow took his examples 

 and it recalled to my mind a type of fossil stem which is found in the 

 St. John exposures of the Dadoxylon sandstone and more frequently in 

 those at Lepreau. I do not remember to have seen this species of a 

 diameter greater than three to six inches, whereas the distinctly ringed 

 ii'unks of D. Ouangondianum attain three or four times the former 

 diameter. Even where occurring in close association with Dawson's 

 ppecies this one is often dark coloured and silicified when the former is 

 more or less infiltrated with calcite and so of a paler hue. This species 

 was not described by Sir Wm. Dawson. 



As showing more distinctly the annular growth of Dawson's species 

 I append here a detailed description of one of the cotypes in the author's 

 cabinet studied by Sir William Dawson, a section of which is in the 

 museum of the Natural History Society of New Brunswick. (See 

 plate I.) The tree was about ten inches in diameter and is more than 

 or less injected with calcite; this mineral has pushed apart the layers in 

 certain parts of the tree, and pressure has distorted the tree and changed 

 it from a circular form to a somewhat quadrate shape, as seen in cross- 

 section. Certain bands have been more freely infiltrated with spar than 

 others, and in the central part of the tree the layers of wood have been 

 much disorganized. The pressure of the enclosing sediments has also 

 had its effect, crushing the trunk in, from one side; and to this cause 

 also may be ascribed the crumpled margin of the central pith cylinder 



1 Notes on North American species of Dadoxylon by Prof. D. P. Penhallow, 

 Trans. Roy. Soc. Can., Sec IV, 1900, pp. 51-79. 



