148 



Transactions of the 



[Monlhly Micrnscoplra! 

 Journal, Warcli 1, 18"0. 



oval, like those of tree ferns, and so are more probably leaf scars ; 

 while the small linear scars would indicate ramenta or small aerial 

 roots. He accordingly restores it as an arborescent form bearing 

 two large fronds, one on either side of the stem (p. 448), 



The scar differs somewhat in form, being in some species 

 circular, but in the majority more or less oval. It is always in the 

 form of an inverted cone, though from the great pressure to which 

 the stems have been subjected it is generally flattened. The actual 

 depth is shown in a specimen of U. minus, found by Mr. C. 

 Peach at Eedhall Quarry, near Edinburgh, which is an amorphous 

 cast in white sandstone of the outer surface of the stem. One of 

 the pits of the natural size is represented in Plate XLIII., Fig. 3. 

 The base or centre of the pit presents a scar of different form in 

 the different species. In U. jMrmatum it has a double 'horse-shoe 

 shape ; in U. StoJcesii it is a half-oval ; in U. Taylori it is circular ; 

 and so on. The figure is formed by a number of small pits repre- 

 senting the number and position of the vascular cords which 



supplied the supported organ. The re- 

 mainder of the scar is covered with single 

 pits, or radiating furrows arranged in 

 symmetrical order around the basal scar. 

 The pits are confined to the lower half 

 of the scar, and the furrows to the upper 

 half. That this is their true position has 

 been already determined by the direction 

 of the leaves when present, and by the 

 form of their scars when they have fallen. 

 I was enabled to establish it still more 

 from the examination of an interesting 

 dichotomously dividing stem in the col- 

 lection of Daniel Koss, Esq., of Rock- 

 ville, near Edinburgh, in which the posi- 

 tion of the scars to the direction of 

 the stem was clearly seen. There is 

 not the slightest indication of scales in any of the large series of 

 specimens I have examined. In attempting to make obvious what 

 authors believed to be there, the drawings of Ulodendron fre- 

 quently exhibit scale markings. Take, for example, the drawings of 

 Allan's specimen of U. parmatum preserved in the Museum of 

 the Eoyal Society of Edinburgh. The original drawing by Allan, 

 though rude and turned upside down, is more accurate than Buck- 

 land's greatly reduced drawing * made from a plaster cast ; or even 

 than the original drawing by Brongniart, in his * Hist. Veg. Foss.,' 

 vol. ii., plate xxviii. In addition to examining the original specimen 



* ' Gcol. and Min.,' pi. Ivi., fig. 3. 



Dichotomously divided Stem of 

 Ulodendron parmatum. 



