18 THE OLDER MESOZOIC FLORA OF VIRGINIA. 



Formation and locality. — Found only at Clover Hill, in the strata asso- 

 ciated with the main coal. 



FILICES. 



Macrot^eniopteris, Schimper. 



Macrotasniopteris magnifolia, (Rogers) Schimper. 

 Plate II, Fig. 3 ; Plate III, Figs. 1 to 3 ; Plate IV, Figs. 1 to 4 ; Plate V, Figs. 1 to 4. 



Fronds simple, and those of the larger plants attaining the length of at least 1 

 meter and the width of 17 centimeters. Young fronds, according to stage of growth, 

 varying in length from 5 to 40 centimeters and in width from 2J to 5 centimeters and 

 over. Outline of the adult fronds of two principal kinds, viz., oblong-spatulate and 

 oblong-lanceolate ; the first is bluntly rounded and broad at the end, and the second 

 gradually narrowing with an elliptic extremity. Margins of the fronds thickened and 

 having towards the summit a very regular sweep, but towards the base gradually 

 approaching the midrib with a more or less undulate or irregular outline, and at the 

 base closing in rather abruptly upon the midrib, the lamina on one side being usually 

 more prolonged than on the other. Young plants in the early stages of growth are 

 broadly elliptical in outline. The epidermis of the frond is usually thin except near 

 the midrib, where it is so thick as to hide the insertion of the lateral nerves, and thus 

 add to the apparent width of the midrib. Midrib of adult plants broad and flat, with 

 comparatively few woody bundles, which appear as strong stride on the surface of the 

 midrib, tapering gradually to the summit ; that of the younger plants, broad to about 

 the middle of the frond, and then suddenly and greatly narrowed. Lateral nerves 

 springing from the midrib under an acute angle, but immediately after their emer- 

 gence becoming perpendicular to it, and thence continuing parallel to one an other and 

 perpendicular to the margin of the frond, about one-half millimeter distant from each 

 other, either not forking or forking close to the midrib, the branches very slowly 

 diverging and soou becoming parallel to each other and to the adjoining nerves. In 

 rare cases the nerves which are not forked in their lower portion branch at some dis- 

 tance from the midrib. The lateral nerves are apparently single nerves, but are really 

 nerve-bundles, composed of two or three fine nerve-strands so consolidated as to appear, 

 under ordinary conditions, as a single nerve. 



Fructification not clearly made out, but apparently composed of elliptical sori, 

 placed either in a single row on the midrib or in two rows, one ou each side of the 

 midrib. 



This magnificent plant has been well described by Professor Rogers 

 in his article "On the Age of the Coal Rocks of Eastern Virginia," pub- 

 lished in the "Transactions of the Association of American Geologists and 

 Naturalists." Professor Rogers gives three measurements of sizes often found 

 in the fronds. They may be distinguished as fronds A, B, and C. Dimen- 

 sions of frond A: Width, 2.4 inches; estimated length, 14 inches. Frond 



