THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 49 



how these longitudinally furrowed stems simulate the ribbed character of Sigillaria.* A 

 similar warning has been given by the late Professor Williamson t in regard to the 

 Arran stems, of which some published accounts refer them to the Sigillarize, although 

 all the evidence in the case is diametrically opposed to such a supposition. 



Description of Specimens. 

 Sigillariostrobus, Schimper. 



1870. Sigillariostrobus, Schimper. Traite d, paleont veget., vol. ii. p. 105. 

 1888. Sigillariostrobus, Zeiller. Flore foss. Bassin houif. d. Valenciennes, p. 391. 



Description. — Cones borne on deciduous peduncles, with few leaves or the leaves 

 reduced to bract-like structures, cylindrical, composed of a ligneous axis bearing spirally 

 arranged sporiferous bracts. Bracts rhomboidal, acute, or long-lanceolate, acute with 

 an expanded rhomboidal base, caducous. Microspores contained in the hollow inflated 

 base of the bract, 0*75 mm. to 2*00 mm. in diameter, smooth, or the surface apiculate ; 

 under surface marked by three ridges radiating from a central point (microspores 

 probably present, but their existence not yet definitely proved). 



Whether the cones of Sigillaria bore microspores as well as macrospores is at 

 present not conclusively settled, and in an earlier part of this paper reference has been 

 made to the opinions expressed on this point by Mods. Zeiller.| I am, however, 

 strongly of opinion that the Sigillarise were heterosporous, and this view is very much 

 founded on the specimen figured on pi. ii. fig. 1. 



This fragment shows a small portion of a Sigillarian cone which hits apparently been 

 split longitudinally ; the upper part of the bracts being embedded in the matrix, they 

 only show their basal extremities exposed on the surface of the rock. The part which 

 came off this fossil must have contained the axis and other half of the cone, but this 

 unfortunately has not been found. 



In examining this specimen the first point that arrests one's attention is the great 

 difference in the size of the bases of the lower and upper bracts. The bases of the lower 

 bracts marked a, pi. ii. fig. 1, are about 3 mm. wide, while the upper ones marked 

 b, c, e, on the figure are about 5 mm. wide. The bases of the smaller and lower 

 bracts are covered with small, smooth macrospores (fig. la x 4) about 075 mm. in 

 diameter (fig. laa x 8). These lower bracts bear the macrosporangia. 



The most interesting part of this fossil is, however, the upper bracts. These, as 

 already stated, have larger bases, and are in an equally fine state of preservation. 

 When their upper surface is examined under the microscope it is found to be distinctly 



* Geological Survey of Canada. Montreal, 1873, p. 41. 



t Williamson, " On the Organisation of the Fossil Plants of the Coal Measures," part x., Phil. Trans., 1880, 

 part ii. p. 494 



% Ante, p. 43. 



VOL. XXXIX. PART I. (NO. 5). K 



