44 PENH ALLOW AND DAWSON 



were cast upou the beach. These fragments, instead of showing any well-connected 

 structure, as in N. Logani, most generally break up into the individual cells, of which only 

 the siliceous casts, to which fragments of the carbonized cell wall remain attached, appear. 



The structure of Nematophyton is unique ' ; at least there is no modern plant with 

 which it is strictly coniparablt\ Nevertheless, the loose character of the entire structure ; 

 the interminable, interlacing cells ; and, finally, their branching into a secondary series 

 of smaller filaments, at once point with considerable force to its true relationship. That 

 it is an alga, admits of no doubt ; and so far as the structrire alone will permit a final 

 decision, its affinity with the Laminariaceœ, as first pointed out by Mr. Carruthcrs, who, 

 therefore assigned it to the genus Nematophytus, appears to be highly probable. 



Recently, Sir Wm. Dawson has modified his original views with regard to the nature 

 of Profotazites, and now assigns to it the name of Nematophyton,' a name which we have 

 retained in the present paper. 



Associated with N. Logani, Sir AVm. Dawson found a few small specimens of another 

 fossil wood which he at first supposed might be a branch or root. An examination under 

 the microscope, however, shows the structure to be, in some respects, quite distinct from 

 N. Logani. 



There are no concentric layers, nor are there any radial openings. The cellular ele- 

 ments are the same, but miich more loosely disposed (Plate II, figs. 7, 8). The large 

 tubular cells are non-septate, interminable, interlacing, and devoid of structixral markings. 

 In diameter they vary from 15 jx to 31 yu, and are, therefore, essentially the same as those 

 in N. Logani, birt, comparatively, they are very remote, and the large intercellular areas 

 are filled in with a much more highly developed mass of fine, interlacing filaments, the 

 diameter of which varies from 5.5 n to 6.3 /<. While, therefore, the two agree in their 

 main characteristics, there is a sufficiently marked difference to justify us in assigning 

 the last to a distinct species, for which we would suggest the name Nematophyton laxum. 



It only remains for us to summarise our results by including a description of the 

 species so far as recognised. 



Genus.— NEMATOPHYTON, Dn. 



Prototaxites, Dn. 



Nematophycus, Carr. 



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

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

 and thick-walled cells, which branch into an intercellular system of small and closely- 

 woven filaments. 



1. — N. Logani, Dn. — Stem distinguished by its concentric layers, which simulate an 

 exogenous structure ; irregvxlar and disjointed radial openings of variable length, 

 and a thin cortical layer appearing in the form of coal. 



' The possibilitj' of a connection between Paehytheca a,n<i Nematophyton, as pointed out by Sir Wm. Dawson, 

 Mr. Carruthers and Mr. Etberidge, is of interest. These pecuhar fruit-like bodies, together with certain laminated 

 fossils found associated with iVema<qp/ti/toi, are now being examined, with a view to determining their possible 

 relationship. ^Qg^j jjjgt^ ^f Plants, 21, &c. 



