DESCRirXION OF THE SrECIES. 281 



Only one specimen was found. On tlie branch preserved on the left 

 side of the figure only two leaves are to be seen borne on the summit ; 

 but this is no doubt due to the fact that the lower leaves have been acci- 

 dentally removed. 



ACACI.fEPHYLLUM VARIABILE, sp. nOV. 

 Plate C'LXX, Fig. 7. 



• Leaves small, variable in shape, ranging from narrowly elliptical to 

 subspatulate and broadly elliptical, often inequilateral, placed spirally and 

 very obliquely on the stem, with long petioles; leaf-substance compara- 

 tively thick and hiding the nerves; nervation as given in the generic 

 description, but not distinct; primary nerv^es .slender; ultimate nerves not 

 seen. 



Locality: Covington street, Baltimore ; rare. 



PROTE.EPHYLLUM, gen. nov. 



I grouj) under this head a number of leaves with a very archaic type 

 of nervation that occur in the Potomac flora. Li their nervation, and in 

 many cases in the form of tlie leaves, they bear a greater resemldance to 

 species of Protea than any other plants. Tlie main points that characterize 

 them are the absence of any pronounced difference in the size of the pri- 

 mary nerves, the great slenderness of these, the lax and irregular reticulation 

 formed, and the uniformly strong ultimate nerves, which give a reticula- 

 tion that reminds one of ferns. Indeed, I was for some time in doubt 

 whether some of these leaves were really angiosperms and not ferns. 

 There are two types of these leaves, that differ only in the presence or the 

 absence of a distinct midrib; when the midrib is present the leaves assume 

 an elliptical form ; when it is absent, they tend to take an orbicular shape. 

 We might perhaps divide the genus into two subgenera according to this 

 distinction, giving one the name roUmdatum. and the other the appellation 

 elongation. 



The genus may be described as follows : Leaves orbicular or elongate 

 in form ; in the case of the former, no midrib present ; in the case of the 

 latter, a thick, vaguely defined, and apparently somewhat succulent midrib 



