13 



that it may constitute a distinct genus. In 1889, in Philosophia 

 Botanica he actually proposed it as a genus, Gaertneria. Unfor- 

 tunately there is a Gaertnera of Schreber of the same year. In 

 1793, Cavanilles described the new genus Franseria. Most 

 authors have regarded Gaertneria of Medicus and Franseria of 

 Cavanilles the same. The genus has been known mostly under 

 the latter name. O. Kuntze was the first one in later years who 

 took up the older name Gaertneria, but he dates it from 1775 the 

 year when Medicus first discussed the species, but as he did not 

 propose a new name for it, but still retained the species in Am- 

 brosia, this cannot be regarded as publication; and Gaertneria 

 might be antedated by Gaertnera Schreber. However, a new 

 question arises. 



The only character separating Xanthium and Franseria is the 

 distinct bracts of the staminate heads in the former and the united 

 ones in the latter. In one species of Franseria the bracts are 

 only united at the base and this character might not be generic. 

 In other respects the original Franseria is very closely related to 

 Xanthium, having many numerous and hooked prickles and 2-4 

 beaks on the fruit, of the character of those in Xanthium, while 

 the most species that have been included in Franseria are closely 

 related to Ambrosia. As stated before. Ambrosia has only one 

 beak that is scarcely oblique at the apex and usually 3-4-toothed. 

 This character is also found in two North American species of 

 Franseria, but all the other species have 2-toothed, very oblique 

 beaks as in Xajithium. Some have one beak, some two or even 

 as many as six or seven. The question is whether the number of 

 beaks, the number and structure of the spines are not just as 

 good generic characters as the number of series of spines and the 

 union or non-union of the bracts of the staminate heads. If such 

 combinations are made the genus Franseria should be divided into 

 se\'eral genera. Such species as Franseria acanthicarpa, tenui- 

 folia and bipinnatifida differ very little from Ambrosia, the 

 distinction being in consisting only of 2-4 series of spines instead 

 of single ones and an oblique 2-toothed beak. The general 

 habit is that of Ambrosia and the staminate heads essentially 

 identical. Such species as Franseria discolor and tomentosa are 



