natural Family of Plants called Composi/a; 83 



vessels there arc generally several in the cord : in Ilelianthiis mnl- 

 iifloriis, however, 1 have not been able to find more than one, either 

 in the trunk of the nerve above the insertion of stamina, or in the 

 branches of the lacinia;. It will be of some interest to verify this 

 fact (which I by no means give with absolute confidence), both 

 on account of the apparently formidable objection it presents to 

 the theory in question, and also that, in following it up by an 

 examination of the point of division, a clearer idea may be ob- 

 tained of the ramification of spiral vessels than has hitherto been 

 given. 



My second objection to M. Cassini's account is, that he de- 

 scribes the nerves as marginal through their whole length. 1 have 

 formerly, in the passage already quoted, stated them to be pa- 

 rallel and approximated to the margins of the laciniae. Perhaps 

 in no instance can the branches be considered as strictly margi- 

 nal ; in many cases they are manifestly distinct from the mar- 

 gins, and in the genus Hymenopappus are further removed from 

 them than from the axis of the laciniae. In H. scabiosaus there is 

 also an evident inequality of the two branches in each lacinia, 

 the stronger extending nearly to the apex, while the weaker either 

 entirely disappears before it reaches the stronger, or unites with 

 it considerably below its termination. In H. ienuifolius this irre- 

 gularity is still greater; one branch being not unfrequently alto- 

 gether wanting, and even the remaining branch considerably weak- 

 ened : where this happens a secondary vessel is always produced, 

 though very few flosculi are furnished with five complete middle 

 nerves. 



To the fact stated by M. Cassini that the lateral nerves are 

 always simple, I have met with only one apparent exception, in 

 an unpublished species of Madia, where they are connected by a 

 few branches with the secondary or middle nerve, which in this 



M 2 plant 



