DESCRIPTION OF THE SPECIES. ] 75 



to the rachis on the upper side and touching each other, or united at base, 

 attached Ijy the entire base, nerves in part forking. 



This genus is represented in the Potomac flora doubtfully by one spe- 

 cies, which has in some respects a different character from the typical 

 forms, such as ClenophijllHm Braunianum Schimper. 



CtENOPHYLLUM LATIFOLIUM, sp. nov. 

 Plato L.XA'III, Figs. 2, 3. 



Leaf very large and wide-spreading ; length of leaflets not disclosed, 

 width in the same portion of the leaf variable, ranging from 27""" to 35'""'; 

 leaflets alternate, going off in the lower part of the leaf at a large angle, 

 in the upper portion much more oblicjue, attached by the entire width of 

 the widened base, which is decurrent and meets the expanded base of the 

 adjacent ones, forming a broad rounded sinus, those of the upper poi-tion of 

 the leaf united more and more, all curved slightly upwards towards the 

 summit of the leaf ; tips of the leaflets not seen ; nerves very strong, 

 going off obliquely at their insertion in the lower and middle portions of 

 the lower leaflets, but nearly at right angles in the upper portions, and all 

 turning strongly outwards to enter the leaflets ; nerves of the uppermost 

 leaflets all oblique ; the nerves fork at the insertion or are simple and par- 

 allel ; occasionally but rarely those simple at base fork somewhere higher; 

 under a strong lens the nerves are seen to be composed of two closely 

 placed nerve-strands which form a flat nerve-bundle. 



Locality : Fredericksburg. 



This splendid plant is very rare; only one specimen was seen. As 

 found in the rock, it was as is depicted in Fig. 2, and probabh- the speci- 

 men depicted in Fig. 3 was attached to the top of it, for it is clearly the 

 sunnnit of tlie specimen given in Fig. 2. But in loosening the imprint in 

 tlie (piarry it was much broken up. The leaf originally must have been 

 of huge dimensions, for the parts seen are clearly but a small portion of it. 

 Tlie plant shows an irregularity in the size of the leaflets, for in Fig. 2 the 

 right-hand lower leaflet is much wider than the adjacent ones. The mid- 

 nerve is stout and rounded. The leaf must have been over a meter in 

 length. This species is strikingly like the large Ctoioplujlla of the Rhjetic 



