74 ROYAL SOCIETY OF CANADA 



already insisted on in my Geological History of Plants, that even in the 

 Sigillarias proper we have probably two types of organization, one 

 approaching to that of Os^cads and Cordaitea? and the other allied to 

 Siîcillariœ- In other words, that the dividing line between Gymnosperms 

 and Acrogens or Archegoniatœ falls within the great genus Sigillaria. as 

 now held by palœobotanists.' 



In proof of this I may refer to the structure of an axis described by 

 me in 1871, and taken from an erect ribbed Sigillaria, undoubtedly of 

 that genus, and probably allied to, if not identical with, my *S'. Brounii. 

 I have described the details of this structure in the paper referred to, 

 and may here merely refer to the figures of the more important tissues and 

 invite attention to their resemblance to those of Cordaiteœ, as figured by 

 Eenault and other French botanists, and to those of modern Cycads. 



It may, however, be doubted whether this axis may not have been 

 introduced accidentally into the trunk in which it was found. This 

 would be in the last degree improbable in the case of a trunk not filled 

 with foi'eign debris, but containing along with sand apparentlj^ only 

 fragments of its own interior tissues. Farther, in many erect trunks at 

 South Joggins there are masses of mineral charcoal on the bottom, which 

 have fallen in before any foreign matter entered, and which, when pre- 

 pared by nitric acid and examined microscopically, show similar struc- 

 tures, as I have shown in my paper of I860 on Vegetable Structures in 

 Coal.^ These observations confirm the im])ression that this structure, 

 much more advanced than that of any Cryptogams, recent or fossil, was 

 that of many at least of the Sigillarian trees. 



But another and less advanced structure comparable with that of 

 Lepidodendra is also found. Of this an excellent example was discovered 

 by Mr. Albert J. Hill in the coal measures of the Cumberland basin 

 in Xova Scotia, and was described b}^ me in 1877. It was an erect 

 ribbed Sigillaria, with broad ribs like *S'. reniformis, and twelve feet 

 in height, filled with sandstone, but having its axis perfectly firm in cal- 

 cite, and standing, like a pole or the core of a casting, erect in the stem, 

 nearly from the base to the summit, though fallen a little to one side. 

 It will be seen that its structure corresponds with Diploxylon of Corda, 

 and with those more advanced Lepidodendroid stems which have thick 

 development of radiating tissue.' 



' Journal Geological Society of London, Vol. XXVII. 



2 Quart. Journ. Geol. Soc, Vol. XV. 



^ Note on a specimen of Diploxylon, Quart. Journ. Geol. Soc, Vol XXXIIL 



