448 THE AMERICAN NATURALIST [^'oL. XLI 



any previous collection from the Don, the leaves contained in the 

 present one are sufficiently characteristic to make the determin- 

 ation reliable. 



Platanus occidentalis L. — One small and imperfect leaf shows 

 the characteristic venation of the sycamore. Although not often 

 represented, this tree has nevertheless been found in a previous 

 collection representing two localities, and it is a recognized con- 

 stituent of the Don flora. 



Hollick ('06, 231, 232) has shown the occurrence of P. aceroides 

 Goepp., together with another large leaved but unnamed species, 

 in the Sunderland Formation of Maryland. 



Populus grandidentata Michx. — This well known but sparingly 

 represented species is a well recognized element of the Don flora, 

 and it once more appears in the present collection. 



Prunus sp. — The genus is represented in the present instance by 

 a single drupe of an oblong form. A similar but somewhat shorter 

 fruit has been found on one previous occasion. 



Quercus alba I^. — The white oak is represented in the present 

 collection by fragmented but well characterized leaves. This 

 species has been observed previously in only one collection. The 

 specimens obtained from Gaol Hill were so imperfect as to make 

 the determination open to some question, but the present material 

 is sufficiently perfect to remove all doubt. 



Other oak leaves are also embraced in the 1900 collection, but 

 the fragments are too incomplete to justify reference to a particu- 

 lar species. It is quite probable that they may represent the 

 white oak, but this cannot be stated with any degree of certainty 

 since the Don flora embraces no less than seven recognized species, 

 any one of which they may be. 



Under the name of Quercus pseudo-alba, Hollick ('06, 227) 

 describes an oak from the Sunderland Formation of Maryland. 

 The leaves which he figures bear a very close resemblance to those 

 from the Don, and it is not unlikely that they may be the same, 

 but a close comparison of more perfect specimens should be made 

 before final decision is reached. 



Robinia pseudacacia L. — A few leaflets of the common locust 

 are found in the present collection. This species appears to be 

 rather sparingly represented in the Don flora, since this is only 

 the second time it has been found. 



