DENBIGHSHIRE GRITS, NEAR C0RWEN, NORTH WALES. 



491 



other things, a new genus which he called Prototaxites, and the 

 species Logani ; he considered this to be the oldest known fossil 

 tree in America, and, as such, gave it the name of Prototaxites, 

 believing that it belonged to the Taxineae. Subsequently (1863), in 

 vol. xix. of our Journal, he described other fossil plants from the 

 Gaspe Devonians ; and apparently the same or a similar fossil is again 

 described under the name of Nemaioxylon crassum. 



Specimens of this plant (Prototaxites) were subsequently examined 

 by Wm. Carruthers, Esq., E.R.S., who pronounced it to be a colossal 

 Alga, or seaweed, and named it Nematophycus. Mr. Carruthers 

 published an important paper upon this plant, wherein he gives his 

 reasons for widely differing from Dr. Dawson *. 



Immediately on the receipt of Dr. Hicks's specimens, and knowing 

 how large a problem depended upon a right interpretation of the 

 structure and affinities of the plant-remains, through their strati- 

 graphical position or age, I at once obtained Mr. E. T. Newton's aid in 

 preparing microscopical sections. The result has been in the highest 

 degree satisfactory ; and he at once determined these remains from 

 the Denbighshire Grits of Pen-y-Glog to be the Nematophycus of 

 Mr. Carruthers. 



Mr. Newton and myself have microscopically examined several 

 sections of both the lighter and darker portions of the carbonaceous 

 matter placed at our disposal by Dr. Hicks ; and we feel convinced 

 that they both present the same structure, the difference seen being 

 almost wholly due to the fact that the intensely opaque nature of 

 the carbonaceous matter in the darker specimens obscures the 

 structure. Mr. Newton's observations were therefore made upon 

 the light-coloured specimens, which we have carefully examined 

 together. When examined with transmitted light and with a low 

 power, the fragments show that the fibrous appearance is due to 

 a number of dark rod-like tubes or cells running in a longitudinal 

 direction, but in a more or less vermiform or wavy manner, some- 

 times closely packed together (fig. 2), sometimes more widely 

 separated : these tubes or cells have one general direction, and 

 consequently appear nearly parallel ; but closer examination shows 

 that other cells irregularly curve in and out of plane, and are not 

 parallel. 



In many parts a dark and apparently granular substance seems 

 to fill the tubes, and may be resolved into round globules varying in 

 size (fig. 3). 



In certain favourable spots some of the tubes appear to be crossed 

 by very fine transverse lines (fig. 4) which strongly resemble spiral 

 fibres ; these lines, however, may be due to the nature of the mineral 

 which fills the cells. On others a network of fine lines may be 

 seen spreading over the tubes ; these might be thought accidental 

 but for their frequent occurrence. In transverse section (fig. 1) the 



* Trans, of the Royal Microscopical Soc, Monthly Microscopical Journal, 

 1872. 



