Maryland Geological Survey 457 



lar teeth and is -undoubtedly referable to this same species another leaf 

 of which is preserved alongside of it on the same piece of clay. There 

 is no obvious relation to Celastrophyllum the absence, of a definite midrib 

 at once removing that genus from consideration. The plant evidently 

 was stemless from a rootstock as the larger specimen figured would indi- 

 cate and was evidently a semi-aquatic marsh plant comparable with 

 Enocaulon, Fontaine's comparison with Plantago emphasized by the 

 name being particularly unfortunate. 



Occurrence. — Patapsco Formation. Federal Hill (Baltimore), 

 Maryland. 



Collections. — U. S. National Museum, Goucher College. 



Subclass DICOTYLEDONAE 



Order SALICALES 

 Family SALICACEAE 



Genus POPULUS Linne 

 [Sp. PL, 1753, p. 1034] 



Trees with narrow lanceolate to broadly orbicular, alternate, stipu- ' 

 late, generally long petiolate leaves. Margins sometimes entire but 

 usually toothed in various ways. Venation pinnate in the modern and 

 in a large number of the fossil species, the secondaries being approxi- 

 mately parallel and the basal pair not of sufficiently disproportionate 

 size to be termed primaries. In numerous fossil species, however, 

 especially those from the Arctic regions and from the earlier American 

 deposits, the basal secondaries are prominent and curved upward, war- 

 ranting the use of the term palmate in describing tliem. Fruit a 2 to 4 

 valved capsule, the enclosed seeds with a conspicuous long coma of 

 white silky hairs, both fruit and seeds occurring as fossils under 

 especially favorable conditions of preservation. 



The genus Populus is an important one for the paleobotanist with 

 over 150 described species, the oldest of which, the celebrated Populus 



