26 J. W. Dawson on Paleozoic Rhizocarps. 



It is true that these are much larger than the sporocarps above 

 referred to, but on examination of G-aspe specimens in my collection, 

 I am disposed to suspect that they also may prove to be the fruc- 

 tification of Rhizocarps. 



It remains to enquire, Are there any Erian plants known to us 

 in their stems and foliage, to which such organs of fructification 

 as those above described might have belonged ? 



A preliminary question would naturally be as to the vegetative 

 organs of modern Rhizocarps. On reference to the descriptions, 

 and to a somewhat extensive collection of specimens placed at my 

 disposal by Mr. D. A. P. Watt, of Montreal, I find that these may 

 be referred to three leading types. Some, like Pilularia, have simple 

 linear leaves ; others, like Marsilea, have leaves in verticils and 

 cuneate in form; while others, like Azolla and Salvinia, have 

 frondose leaves more or less pinnate in their arrangement. The 

 first types present little that is characteristic, but there are in the 

 Erian sandstones and shales great quantities of filamentous and 

 linear objects which it has been impossible to refer to any genus, 

 and which might have belonged to plants of the type of Pilularia. 



It is possible also that such plants as Psilophyton glabrum 

 and Cordaites augustifolia, of which the fructification is quite 

 unknown, may have been allied to Rhizocarps. With regard to 

 the verticillate type, we are at once reminded of Sphenophyllum, 

 which many palseo-botanists have referred to the Marsiliacoe, 

 though, like other palaeozoic acrogens, it presents complexities not 

 seen in its modern representatives. S. primaevum of Lesquereux 

 is found in the Hudson River group, and my S. antiquum in the 

 middle Erian. Besides these there are in the Silurian and Erian 

 beds, plants with verticillate leaves which have been placed with 

 the AnnularicBj but which may have differed from them in fructi- 

 fication. Annular ia laxa of the Erian and Protannularia Hark- 

 nessii of the Silurian may be given as examples. As to pinnate 

 leaves, I have already referred to the remarkable plants of the 

 genus Ptilophyton, found both in the Erian and Carboniferous, 

 and which seem to have been aquatic in their habit like Rhizo- 

 carps. It is deserving of notice, also, that the two best known 

 species of Pt do phi/ ton (P. princeps, and P.robustius), while allied 

 to lycop jds by the structure of the stem and sucb rudimentary 



