472 MF.SOZOIC FLORAS OF TNITED STATES. 



CycADEOIDEA Cl.ARKlAXA Waicl 11. sp. 



PI. LXXXIX. Figs. I, 2. 4: PI. ('VI. 



Trunks raliier large, tall and subcvlindrical or barrel-shaped, laterally 

 compressed, unbranched; rock rather hard, of a light-ash color and 

 average specific gravity; organs of the armor horizontal or somewhat 

 descending; rows of scars from left to right making an angle with the 

 axis of 45°, those from right to left an angle of 80°; leaf scars subrhombic or 

 irregular in shape and varialjle in size, 15 mm. to IS mm. wide, 10 mm. to 

 15 mm. high ; leaf bases present, sunk about 1 cm. below the surface, porous; 

 vascular bundles not visible on the cross sections, but distinct on the eroded 

 surfaces ; ramentum walls very thin and sharp edged, thickening below to 3 

 mm. to 5 mm. hard, destitute of markings or division line Ijetween the 

 plates; reproductive organs obscure and reduced to pitted areas on the 

 eroded surface; armor 3 cm. thick, the leaf bases passing insensibly into 

 the woody axis ; wood 2 cm. thick, in four layers or rings; outer layer 1 cm. 

 thick, chiefly composed of the elements of vascular tissues passing upward 

 and outward through it and curving over at the outer margin to enter 

 the deflexed leaf bases; fibrous zone of three rings, the outer and inner 

 consisting of loose, open tissue, largely decayed in the only specimen that 

 shows them, leaving a fissiu'e, the middle ring hard and firm, forming a 

 plate surrounding the medulla, 5 mm. thick, its inner surface regularly 

 marked with the scars of the medullary rays, which are elliptical in shape 

 and disposed in alternating rows; medulla very large and prominent, 

 elliptical in cross section, thickest in the middle of the trunk to conform 

 to its shape, which it chiefly determines, the shorter diameter varying 

 from 9 cm. to 15 cm. and the longer from 14 cm. to 18 cm., coarse grained 

 and homogeneous in structure, its surface where exposed handsomely 

 marked by the ridges and flutings of the bases of the medullary rays 

 rising out of it. 



This species is known by two of the later acquired specimens, the 

 Whitehead trunk, \o. 1, M. G. S.-W. C, B., No. 9050, and the R. T. 

 Donaldson trunk, No. 2, M. G. S.-W. C, B., No. 9052, both found in 

 the Patuxent Valley south of Laurel, but probably not at the same 

 spot, so as to warrant the conclusion that might be drawn from their 

 appearance that the hitter forms a part of the missing upper portion 



