28 PENHALLOW^ON 



and form a very compact structure which presents a most striking resemUance to the 

 longitudinal structure of the plant now under consideration. 



The rounded openings, observed in transverse section, are here seen to be continuous 

 tubes filled with highly crystalline matter, while the open tracts appear as rounded and 

 small areas of irregular size and form. The branching of the cells has not as yet been 

 determined as fully as might be desired. In only one case thus far haA'e we found the 

 large cells to branch, but this was of so pronounced a nature as to admit of no question. 

 What appear to be secondary filaments, having a diameter abovit one-fifth that of the 

 large cells, have been observed in both transverse and longitudinal sections, in every case 

 appearing in the open tracts above described. "While, therefore, it seems probable that 

 such an intercellular structure exists, I must, for the present, speak with some reserve 

 on this point. 



The " minute dots " on the cell walls, referred to in the original description, cannot 

 be regarded as having any structural significance, and we have so far found the walls to 

 be wholly structureless. Many of the cells show irregularly scattered, dark bodies which, 

 of variable size, are sometimes spherical, again distinctly angular. The material of which 

 they are composed has been so altered as to render their true character a matter of some 

 doubt ; but from what has been observed in the Avarions species of Nematophyton thus far 

 described, it is quite probable that they have similarly originated from spores. 



The evidence thus iar obtained points, with considerable force, to an afiinity with 

 Nematophyton to which genus I would transfer it, retaining the specific name originally 



Genus.— NEMATOPHYTON, Dn. 



Quart. Jn'l. Geolog. Soc. XV, 484 ; Nov., 1862, 299, 30*7, 326 ; Nov., 1863, 466, 46Y ; 

 May, 1881, 302 ; Aug., 1881, 482 ; May, 1882, 104 ; Geolog. Surv. of Can., 18G3, 401 ; 1871, 

 16 and 20 ; 1882, II, 97, 10*7 ; Can. Nat. V, 9 ; VI, 1*77, 179 ; (New Ser.) VII, 173 ; Ann. and 

 Mag. Nat. Hist. 5, IX, 59; M. Mic. Jn'l. VIII, 160; X, m, 208; XI, 83; Quart. Jn'l. Mic. 

 Soc. XIII, 313; Amer. Nat. V, 185, 245 ; Geolog. Hist, of Plants, 21, 42; Trans. Roy. Soc. 

 Can., VI, iv, 27 ; Proc. Amer. Ass. Adv. Sci., 1856. 



Plants of arborescent form from a branching, root-like base. Stem branching, often 

 exceeding 1° in diameter. Structure composed of unjointed, interlacing, structureless 

 cells which In'anc'h into an intercellular system of small and clo.sely-woven filamenis. 



1. — N. LoGANi, Dn. 



Prototaxiles Logani, Dn. 

 Nemalophycuii Logani, Carr. 



Stem distinguished by its concentric layers, which simulate an exogenous 

 structure ; irregular and disjointed radial openings of variable length, and often a 

 thin cortical layer appearing in the form of coal. 



Cells of the medulla, thick-walled, 13 - 35 // in diameter, interwoven, loosely 

 atygregated and turning into the radial spaces. Hyphal structure composed of 

 branching filaments 4-9 /< in diameter, which branch from the cells of the 

 medulla and form a closely-woven intercellular plexus. 



