36 PBNHALLOW AND DAWSON 



would only be a farther extension of the same principle to find a pseudo-exogenous stem 

 of still greater antiquity, constructed wholly or principally of long, tortuous fibres similar 

 to those in some lichens and algae, from which, however, I regard the tissues of Nemato- 

 phyton as essentially distinct. It is farther to be observed that since Nematophyton 

 extends downward from the Lower Devonian, and antedates any known Conifer, it belongs 

 to a time as much older than the coal formation, as this is older than the Cretaceous, and so 

 to a far earlier period of the earth's history. Thus it may represent a leading type of forest 

 vegetation in the Silurian and early Devonian, and which disappeared before the intro- 

 duction of the Dadoxylons and other trees of the Middle Devonian and later formations. 

 I have also been disposed to regard it as possibly a iate survivor of a type of vegetation 

 which may have existed even in the Cambrian and Laurentian, and may have been con- 

 nected with the accumulation of the great quantities of carbonaceous matter known in 

 the latter, and with that of the vegetable debris abundant in some parts of the fonner, 

 and which, though it has not yet afforded distinct structure, presents indications of longi- 

 tudinal fibres akin to these of Nematophyton, and appears in similar angular fragments 

 to those representing that type in the Silurian. 



II. — Notes upon the Fossils. [Prof. PenhaUotv.) 



1. — Nematophyton Logani, Dawson. 



Prototaxites, Dn. 



Nematophycvs, Carr. ; Jn'l Geolog. Soc. XV, 484 ; Aug., 1881, 482 ; May, 1882, 104 ; 

 Geolog. Surv. of Can., 1863, 401 ; 18*71, 16 ; 1882, II. 10*7 ; Can. Nat., (New Ser.), 

 VII, 1*73 ; Ann. and Mag. of Nat. Hist. 5, IX, 59 ; M. Mic. Jn'l VIII, 160 ; X, 66, 

 208 ; XL 83 ; Quart. Jn'l Mic. Sc. XIII. 313 ; Amer. Nat. V. 245, 185. 



Early in the winter of 1886-8*7, Sir Wm. Dawson placed several slides of Prototax- 

 ites in my hands, with the request that I should make a careful examination of them. 

 The specimens consisted of several cross and longitudinal sections, all taken from the 

 main stem of the plant, with the exception of one which was cut from what was at first 

 thought to be a branch or root. This we shall deal with separately. Several of the 

 sections — two in particular — were beautifully prepared, and admitted of very critical ex- 

 amination. From them were taken the photomicrographs, illustrating this paper. The 

 others, thicker and more opaque, were used only for the determination of the more gen- 

 eral structural features under a low power. The stem from which these sections were 

 taken, and from which several others have more recently been cvit, for the purpose both 

 of verification and of more extended examination, is designated in the Museum collection 

 as No. 5. 



The literature of the svibject, as cited above, is not very copious. It embraces a 

 paper by Mr. Henry Hicks on the discovery of a plant in the Denbighshire Grits of 

 Wales, which Mr. Carruthers identified as the Prototaxites^ of Sir Wm. Dawson. With 

 this exception, the literature consists chiefly of a discvission between the founder of 

 the genus and species. Sir Wm. Dawson, and Mr. Carruthers, to whom specimens were 



' Nemaiophycus Hicksii of Etberidge, Quart. Jn'l Geol. Soc, Aug. 1881,494. 



