DESORirTlUN OF THE SPECIES. 245 



Localities: Fredericksburg; fishing hut above Dutch G:ip('iuial; riuv 

 This phmt differs from tlie normal .S'. Ilclclienhaclii in the very long and 

 slender leaves. 



Skquoia subulata Heer. 



Plate CXVII, ri^'. 7 ; Plate C'.WIII, ri;;s. T), C. 



Branches comparatively slender, piimately arranged in one plane; the 

 ultimate branches are nearly at i-ight angles with the penultimate stems; 

 leaves obliquely inserted, widest at base, acuminate, very narrow, some- 

 times acicular, very long in proportion to their width, usually closely 

 placed on tlie ultimate twigs, more remote on the older ones, unite<l at l)ase. 



Localities: Fishing hut above Dutch Gap Canal; Fredericksburg; 

 near Telegraph Station. 



'i'he plant is rather common at the Dutch Gap locality, but is very 

 rare elsewhere. PI. CXVII, Fig. 7, gives a portion of an older twig with 

 unusually remote and very narrow leaves. PI. CXVIII, Fig. G, has on 

 the ultimate twigs closeh' placed leaves that are very long in proportion to 

 tlieir width. 



Skquoia ambigua Heer. 



Plate CXVIII, Fig. 2; Plato C'XX, FigH. 1-6; Plato C'XXVII, Fig. .''.; Plate CXXXII, Fig. 3. 



Branches elongate, fully leaved throughout, branchlets alternately 

 grouped; leaves decurrent, short, rather thick, falcate, incurved, acuminate, 

 one-nerved; strobiles globogo in form; scales ])eltate, rather ilat. 



This description which Ileer gives' for his Sequoia onibif/ud, from the 

 Kome beds of Greenland, and his figures agree so closely with certain of 

 tlie Potomac conifers, that there seems to be no doubt that this plant is found 

 in the Potomac flora also. It may be added, for the Potomac forms, that 

 the leaves are widest at base, narrowly oblong to subtriangidar. 



Localities : Fishing hut above Dutch Gap Canal ; river bank a few 

 yards above the fishing hut; near Telegrajdi Station. 



The plant is ratlier common at the first and second localities, and rare 

 at the third. There are a few points of difference in the Kome and Poto- 

 mac forms, but no greater than might be expected in the same species when 



' Flor. Foss. Arctica, vol. 3, PI. XXI, Figs. 1-11. 



