190 THE roTo:\iAC on youijjger mesozoic flora. 



Tlie bud-scars are of two kinds, which are well shown on the phxte 

 hist mentioned. The hirge scars stand out somewhat from the surface of 

 the trunk, and have a woody axis of varying thickness, surrounded by one 

 oi- more concentric circles of small leaf-scars. These leaf-scars are about 

 one-third the size of the imprints left by the bases of the petioles. The 

 woody axis within these encircling small leaf-scars varies a good deal in 

 size, and some of them, as Carruthers pointed out, are more or less hollow, 

 no doubt being caused by the decay of the axis before silicification took 

 })lace. Tlie.se axes probably bore some kind of fructification. 



Tlie small leaf scars surrounding these axes were probably caused by 

 leaves of small size or bracts, whose bases, like those of the larger leaves, 

 persisted until after the silicification of the material which surrounded them 

 took place and tlien decayed The smaller bud-scars are quite difi"erent 

 from those just described. These too may be seen on PI. CLXXIV. 

 They are considerably smaller than those with the woody axes, and con- 

 sist simply of concentric circles of small leaf-scars like those around the 

 woody cores of the larger scars. They liave no woody axis, and appear 

 to be undeveloped buds composed of small leaves or bracts. There is 

 nothing to show what is the functional meaning of these numerous scars of 

 buds, but it is quite possible that the larger ones may have borne the 

 female inflorescence, and hence trunks such as No. 1 would belong to the 

 female plants. The open pits left by the decay of the bases of the petioles 

 of the principal leaves of the trunks are exact casts of these bases. They 

 seem to have had normally in cross-section a shape that is accurately rep- 

 resented b3' a bow with tlie string bent into an acute angle caused by 

 drawing an arrow to its head, the curving bow representing the upper side 

 of the hollow cast. Owing to distortion they assume sometimes rhombic 

 or elongated triangular shapes. They are smaller towards the top of the 

 stem than towards the bottom, and have an average size towards the bot- 

 tom of the trunks of 18°™ by 8™'", towards the top of 10""" by 5°"°. 



Fkagment No. 1. 



Between Washington and Baltimore was found a large fragment 

 exactly resembling trunk No. 1, but not broken off from that. This resem- 



