DESCRIPTION OF SPECIES. 41 



genus Asterocarpus than any other. They may, with all the greater pro- 

 priety, be placed in this genus, as this is acknowledged to resemble closely 

 Mertensia. Indeed, Weiss thinks that Laccopteris ought not to have been 

 separated from Asterocarpus, and that both much resemble the Gleiche- 

 niacese. My chief reason for separating these plants from Mertensides is 

 the fact that the pinnules are always fully fructified. 



Asterocarpus Virginiensis, spec. nov. 



Plate XIX, Figs. 2-5; Plate XX, Figs. 1, 2; Plate XXI, Figs. 1, 2; Plate XXII, Figs. 1-3; Plate XXIII, 

 Figs. 1-4; Plate XXIV, Figs. 1, 2. 



Frond very large, probably arborescent, rachis sometimes 2£ centimeters thick, 

 tripinnatifid or quadripinnatifid, quite polymorphous. Ultimate pinnae opposite or 

 subopposite. Pinnules of sterile and fertile plants different, all thick and coriaceous. 

 Pinnules of the sterile plant, in the uppermost portion of the frond, or primary pinnae 

 simple, with entire borders, subopposite or alternate, oblong, bluntly rounded at the 

 summit, very slightly falcate, and slightly decurrent, those of normal size 2S milli- 

 meters long and 8 millimeters wide in the middle; terminal pinnules obliquely inserted, 

 decurrent, and united for a considerable distance. Sterile pinnules in proceeding to 

 lower portions of the frond become first undulate on the margins, then crenately lobed, 

 and finally cut into ovate acute lobes, which are separate to below their middle, thus 

 causing the pinnule* to pass into pinnatifid pinna?.. Pinnules of the fructified frond 

 undergoing the same modifications from the upper to the lower part of the frond as the 

 sterile pinnules, but narrower, very thick, and dense, more acute and more distant, 

 decurrent by a broad wing; nerves varying much with the different parts of the plant 

 and the different forms of the pinnules; in the fertile pinnules they are obliterated, 

 except the very thick middle nerve, and single strong lateral nerves bearing the sori. 

 In the sterile pinnules of the upper part of the frond the midrib is strong, but dissolves 

 into branches towards the apex. Lateral nerves of the lower part of the pinnule 

 grouped, three nerves going off from the same point of insertion, the middle one being 

 forked near its base. In the middle and upper part of the pinnules the lateral nerve 

 forks at its insertion, and the upper branch forks again near its base. All the branches 

 are strong, sharply defined, and prominent, and curve strongly outwards to meet the 

 margin of the pinnule. In the undulate and crenulate pinnules the lateral nerves fork 

 so as to form flabellate groups which fill the lobes. In the pinnatifid pinnae of the lower 

 portions of the frond each ovate lobe has a middle nerve which at base is strong, but 

 towards the apex dissolves into branches. The lateral nerves go off iu part from the 

 rachis of the pinna, and also from the middle nerve of the lobe, and are once forked; 

 all are strong and very distinct. Fructification in the form of rounded sori, composed 

 of 5 or 6 sporangia, grouped radially around a central point, and forming two rows, 

 one on each side of the middle nerve. The lower row is decurrent, occupying the wing 

 of the pinnules. Sometimes the sori are found only on the ends of large pinnules of 

 the normal sterile form. These are then much narrowed in the parts occupied by the 

 sori, but otherwise unchanged. 



