Description of a yew Genus and Eleven New Species. 101 



Tire neck is striated longitudinalh', terminates with a rounded point, 

 at tlie base, and is prolonged as a central axis for a distance into the 

 frond. The upper part of the frond possesses no central axis. The 

 lower part of the neck is not celluliferous, farther up small distant 

 cells appear between the strite, these, as we ascend become larger and 

 more numerous, and finally, when the neck may be said to assume the 

 character of a central axis, the cells upon it are arranged between per- 

 pendicular, elevated stride, into rows, which intersect each other diagon- 

 ally'. These perpendicular striie, however, do not extend to either side 

 of the axis, nor beyond it. 



Both sides of the frond are alike celluliferous and tuberculated. The 

 presence of the tubercles destroys the regularity and diagonal 

 arrangement of the cells, which commence at the top of the neck, 

 and hence they are found, on different parts of the frond, arranged 

 crosswise, more or less sharply diagonal, or curving to accommodate 

 themselves to the irregular order and dispersion of the tubercles. The 

 cell mouths are not uniform in shape, many of them are elliptical or 

 somewhat diamond shaped, others are round or oval. The walls be- 

 tween the cell mouths are moderately thick. The cells will number 

 from eight to twelve in a line. The edges of the frond are sharp and 

 perforated, bj- the apertures of minute cells, for a short distance from ' 

 the neck. Above this part, however, the cells appear to preserve their 

 size, almost or quitt to the margin. 



The tubercles are conical, dispersed without order, and usually 

 about a line distant from each other. The summits are solid, or 

 occupied by very minute cells. 



The neck and central axis are each about a half line in diameter; 

 the remainder of the frond, between the tubercles, has only about 

 twice the thickness of ordinary foolscap paper. The specimen figured 

 has a length of 1 6-10 inches, and a width of nearly an inch, but it is 

 not complete either in its length or width. Another specimen, havino- 

 about the same length, and uniformh- expanding from the neck up- 

 ward for a short distance, has a width of 6-10 inch at the distance of 

 6-10 inch from the point of the neck; above this, the expansion is not 

 so rapid, and at the distance of an inch, the width has only increased 

 to f inch. 



The specimen figured is from the collection of Mrs. M. P. Haines, 

 of Richmond, Indiana, and was found in the upper part of the Cincin- 

 nati Group. I have collected specimens of the same species, on the 

 tops of the hills, at Cincinnati. The range of the species may, there- 

 fore, be considered as co-extensive with the upper half of the Group, 

 though good specimens ma}" be \evy rare. 



Bases of Ptilodictya, having nearly the form of bases of Heteroa-imcs^ 

 radiately lined from the point of attachment outwards, are frequently 



