230 Professor Williamson on some [Feb. 16, 



and that it belongs to the Monocotyledons." I long ago expressed 

 my strong doubts as to the correctness of this assertion.* On a 

 recent visit to the Museum of the Glasgow University, my friend, 

 Mr. John Young, showed me one impression of a newly discovered 

 specimen of the same plant which fully justified my scepticism as to 

 its Phanerogamous nature. The opposite and more perfect impression 

 was in the hands of Mr. Robert Kidson, who has since described this 

 and other examples in a paper now passing through the press, but 

 who has not only provided me with impressions of the yet unpublished 

 plates, but has kindly allowed me to copy his figure of the Glasgow 

 specimen in the woodcut (Fig. 9). The fossil is evidently the fructifi- 

 cation of a plant of the Asterophyllitean type, having a jointed stem, 

 a, giving ofi" verticils of short leaves, not only at the nodes of the nude 

 stem (6), but at those (6', h') of the spore-bearing part of the branch.l 

 Unfortunately none of the specimens of Pothosites hitherto dis- 

 covered retain any traces of the internal organisation of their stems. 

 But there is not much difiiculty in determining the general features 

 of this organism. The constrictions, h\ are obviously nodes like those 

 of the naked stem 6, hence the thickened joints, c', correspond to the 

 internodes c. Now none of these Asteropliyllitean plants give off 

 organs of fructification from the internodes. They always spring 

 directly or indirectly from the nodes. Each joint, c', of Fig. 9 is made up 

 of longitudinal lines of Sporangia which can have no organic union with 

 the stem which they invest, save at the node immediately below each 

 joint. In the hitherto known forms, the Sporangia spring directly or 

 mediately from the axils of separate leaves ; but they are frequently 

 supported on separate small branches, which sj)ring in verticils from 

 the node of some larger stem. I surmise that such is typically the 

 case in the Pothosites; only instead of each secondary branch consti- 

 tuting a distinct, free strobilus, as in Volkmannia and other allied 

 forms, these strobili have here coalesced laterally, forming a cylin- 

 drical investment of each internode of the axis — as the free anthers 

 of an ordinary flower have, in the Compositae, coalesced into a 

 cylinder enclosing the pistil. This exj^lanation seems to me to indicate 

 the true place of the Pothosites amongst the Verticillate-leaved plants 

 of the coal-measures. At any rate we learn how great would have been 

 the mistake of any framer of floral genealogies who, trusting to the 

 authority of text-books, made the Monocotyledons originate with 



* * Essays and Addresses, by Professors and Lecturers of the Owens College, 

 Manchester,' pp. 129-30, 1874. 



t Mr. Kidson thinks that the plant is the fructification of the genus Bornea. 

 I am not, however, sure that it can yet be identified with that obscure genus. 

 At present the entire group of these verticillate-leaved Carboniferous plants is in 

 a state of hopeless confusion, from which I fear we shall be long in escaping, 

 since knowledge of the internal structure alone will enable us to determine the 

 types of stem to which they severally belong. At present we are only familiar 

 with those of Calamites, Asterophyllites, and Sphenophyllum, and cannot even 

 identify the leaves of the first two of these genera when detached from such 

 parent stems as retain their internal structures. 



