PSILOPHYTON, ISOETITES. 19: 



of the horizontal creeping rhizomes, and figures of them from Dawson 7 . 

 These when preserved in their natural position fill at Gasp6 certain hard 

 beds of clay, as Stigmariae fill the underclays of coal-seams. They are 

 horizontal creeping stems with occasional bifurcations ; their smooth surface 

 bears here and there small circular scars, from which roots proceed vertically 

 downwards and traverse the beds beneath. Unfortunately there is no 

 figure of a portion of rhizome attached to an evident stem of Psilophyton, 

 though the author states that he has seen entire plants two or three feet 

 long in connection. In his first publication 2 Dawson figured an object of 

 indefinite form having several lobes and attached laterally to a branch, 

 which he explained as the fructification of the plant. In the description he 

 says of it, ' Fructification probably in lateral masses, protected by leafy 

 bracts.' Subsequently 3 the fructifications assume a totally different appear- 

 ance. Small branches with repeated bifurcations, smooth and showing none 

 of the distinctive features of the sp'ecies, bear at their extremities groups of 

 small stalked ovate-lanceolate bodies, sporangia according to Dawson, 

 which open, as he maintains, on one side by a longitudinal fissure. Not 

 only the character of this fructification, but its connection also with our 

 plant, is thus thoroughly obscure and doubtful. In one piece Dawson found 

 anatomical structure preserved. The specimen in question is unfortunately 

 not very fully described, and the figure 4 does not altogether agree with the 

 description of the rhizome to which the fructification was attached. The 

 only transverse section of this specimen figured is oblique in its direction 

 and very imperfect 5 . It seems to contain a central vascular bundle-strand, 

 in which the presence of scalariform tracheides was ascertained, and which 

 is said to be surrounded by a zone of ' woody fibres.' 



The other described species of the genus are in much worse case than 

 Psilophyton princeps. The specimen figured by Dawson 6 as Ps. robustius 

 looks like something very different, and indeed the author himself says that 

 fragments of this species are scarcely to be distinguished from leaf-stalks of 

 Ferns. Bodies of indefinite form set in bunches on the extremities of such 

 stalks or of their lateral branches are supposed to be fructifications. This 

 form is said to be confined to the Upper Silurian formation. The figure 

 of Ps. glabrum in Dawson 7 looks like a fragment of a branched leaf-stalk 

 of some Fern ; that of Ps. elegans 8 shows only some irregular sinuous 

 lines. The same species appears in another and not much better figure 9 

 made up of bundles of these hooked lines. And if the author himself 

 admits so many quite undecipherable remains into his genus, it is not 



1 Dawson (5), p. 479, and (1), vol. i, t. 10. 2 Dawson (5). 3 Dawson (1), vol. i, tt. 9, 10. 

 4 Dawson (1), vol. i, t. 20, ff. 241, 242. 5 Dawson (1), vol. i, t. u, f. 134, and (10), p. 465 ; 



t. 18, f. 22. * Dawson (1), vol. i, t. 12. 7 Dawson (1), vol. i, t. 7, f. 79. 8 Dawson (1), 



vol. i, t. 10, ff. 122, 123. 9 Dawson (6), t. 14, ff. 29, 30.* 



