DESCRIPTION OF THE SPECIES. ' 217 



Localities: Fredericksburg; Baltimore, at Federal Hill. 



Tiie plant is very rare at BaUiinore, but abounds at Fredericksl)ui'o-, 

 where it is by far the most connuon fossil. The great number of specimens 

 of this plant at the latter locality indicates that a forest of it must have 

 grown near by. The existence of well-defined buds shows that the growth 

 of the plant was not continuous, but that periods of repose occurred. In 

 many cases the epidermis of the ultimate twigs is so well preserved that it 

 shows the entire shape and dimensions of the twigs, and may be stripped 

 off from the stone. In such cases there is no trace shown of woody fiber 

 and only a faint imprint is left. The entire material of the smaller twigs 

 was evidenth' pulpy and succulent. Only in the older and larger stems is 

 a small woody axis shown. In all cases the removal of the epidermis car- 

 ried away the leaves, and these leave no scars except on the older 

 twigs. It is quite common to find the shrunken remains of the twigs 

 lying in molds which are now considerably larger than tliemselves, and 

 which they evidently once filled. In twigs 1*"" and under in diameter we 

 may often find the parchment like epidermis perfectly preserved, wrinkled 

 transversely, filled with a brown dust, Ijut showing no woody matter. When 

 woody matter existed it has alwaj-s been changed to jet, involving the total 

 destruction of tlie tissue, so that its structure can not be made out. The 

 woody axis, when j)resent in the form of jet, is always much smaller than 

 the tube of ei)i(k'rinis which inclo.ses it. It is a peculiar ftict that the woody 

 matter of this plant was never found preserving the structure of the tissues. 

 This results, perhaps, from the succulent nature of the material. This de- 

 struction of tissue and softening of the material of the plant may account 

 for some peculiar differences seen in parts which evidently once belonged 

 to the same plant. On some of the older stems, if some of the succulent 

 cortical zone remains, or if the epidermis is preserved, the jointing is plainly 

 shown. (See PI. XCIX, Figs. 2, 3; PI. XCVI, Fig. 3, etc ) 



In other cases, where only the woody axis is preserved or nothing but 

 an imprint is left, no indications of jointing can be seen, although on ulti- 

 mate twigs of the same specimen which retain the epidermis the jointing 

 is plain In the decorticated specimens figured on PI. XCVII, Figs 1, 2; 

 PI. XCVIII, Fig. 2; Plate XCVI, there is no trace of jointing, the softening 



