﻿Bicknell: Ferns and flowering plants of Nantucket 555 



ovate and harshly papillate-pubescent, the other possessing a 

 much finer and closer, even a soft, canescent pubescence, and 

 more or less cordate leaves. In the latter, the Howard Street 

 plant, the larger leaves were deeply cleft into three, or even five, 

 broad overlapping globes, these also deeply lobed and cut; the 

 largest leaves were over 2 dm. in length and breadth, their primary 

 divisions over 12 cm. wide. 



* Ambrosia trifida L. 



A few rather low plants, with unlobed leaves, in waste spot 

 west of the town, August 11, 1906, in full flower; young plants 

 mostly under 15 cm. high, with deeply three- to five-lobed leaves, 

 in a farm yard in Polpis, June 12, 191 1. 

 Ambrosia artemisiaefolia L. 



An abundant weed flowering from late summer doubtless until 

 killed by frost. Represented by several varieties or elementary 

 species differing in leaf pattern and pubescence. 



* Ambrosia psilostachya DC. 



Mrs. Flynn has kindly sent me for examination specimens of 

 this species in full flower and fruit collected by her near Sankaty 

 Head, August 13, 1897. Dr. Rydberg has examined these speci- 

 mens with me at the herbarium of the New York Botanical 

 Garden. They are perfectly typical and are closely matched by 

 numerous examples from the far west. I do not know that this 

 species has ever been recorded from east of Illinois other than as 

 a ballast plant, but it seems quite possible that it may have been 

 making its way eastward unnoticed through its similarity to A. 

 artemisiaefolia. Its presence on Nantucket in a part of the 

 island where unusual introduced plants would scarcely be looked 

 for is not suggestive that it is a wholly exceptional waif in our 

 eastern flora. It is in point that it occurs also on Martha's 

 Vineyard, where I found it along a weedy roadway at Edgartown 

 in full flower September 14, 1910, and in mature fruit October 12, 

 1 911. The only other eastern specimen of wich I have any 

 knowledge is one in the herbarium of the New York Botanical 

 Garden collected on ballast ground at Weehawken, New Jersey, 

 September 6, 1895. But as far back as 1888 the species was 

 included among the ballast plants found in the vicinity of New 



