432 STRUCTURE OF STIGMARIA. 



larger, specimen had been sent to the Museum, by Mr. Ormerod, and 

 figured for me by Mr. Baily. In this latter the cavities are of somewhat 

 less diameter, and contain the obconical or flaggon-shaped bases of the 

 rootlets, whose summits are level with the mouth of the cavity, and are 

 depressed at the apex. 



In neither of these cases could I gain any information upon the par- 

 ticular circumstances under which these valuable specimens were pre- 

 served, to which however they must owe their singularly perfect 

 condition. The precise locality of the specimen, Fig. 3, is unknown : 

 Mr. Ormerod's was found overlying the white coal in the Peel Quarries, 

 Lancashire. 



Comparing these with the usual state of the plant, figured at Plate 2, 

 fig. 4, the amount of collapse of the tissue which shall bring the base of 

 a cavity a full half-inch deep, to the surface, must appear startling ; but 

 it is not really so remarkable as that the whole cylinder, including the 

 vascular axis, should be reduced by pressure from the thickness of three 

 or four inches to that of an inch, or even a few lines, or to a mere flake, 

 as is generally the case with this plant when preserved (if this deserves 

 the name of preservation) in the shales above the coals.* 



While upon this branch of the subject I may allude to the singular 

 difference in the appearance of the surface in different parts of the same 

 Stigmaria. In the Bolton railway trees, to which Mr. Binney conducted 

 me, the Sigmaria roots extended uninterruptedly for upwards of 20 feet, 

 and at different points along that distance from the trunk of one indi- 

 vidual we had many opportunities of marking the appearance of the 

 surface : this, which was characteristic of S. jicoides throughout the 

 greater part of their length, when within a few feet of the tree was seen 

 to be materially altered. The roots themselves here became broader, 

 more vertically compressed, the scars densely packed, and forming 

 transversely elongated areolae, the fossil thus possessing all the charac- 

 ters of S. conferta of Cor da. f 



Though so much swollen below, the surface of attachment between 

 the base of the rootlet and of the cavity into which it is inserted must 

 have been but limited and the union slight ; for in several instances 

 these organs are loose in the cavity, and resemble so closely a nut in its 

 shell, that this fossil has been taken for a fruit with many nuts borne 

 on a pitted receptacle. In the admirable and very complete account 

 of the genus, published by M. Goeppert,{ there is a figure (Table 

 XIII.), representing the outline of the rootlet as produced within the 



* The Stigmaria is rare in the shales ahove the coal ; but I have observed it to occupy 

 that position in the Oakwood level of Cwm Afon (in S. Wales). I have elsewhere (p. 396) 

 given my views on the subject of the prodominance of this vegetable in the underclay. 



t Corda, Flora der Vorwelt, Tab. 13. 



% Goeppert. 



