456 SYNGENESIA. 



can never afford a generic character, pro- 

 vided there be no corresponding genus 

 without them. This must be determined 

 by experience and observation. They are 

 indeed to be considered as a very secondary 

 mark, the most essential in this Class be^ 

 ing derived from the receptacle, crown of 

 the seed, and calyx. These Gaertner has 

 illustrated with the greatest accuracy and 

 skill, but even these must not be blindly 

 followed to the destruction of natural 

 genera. 



4. Polygamia necessaria. Florets of the 

 disk furnished with stamens only, those of 

 the margin, or radius, only with pistils; so 

 that both are necessary to each other. This 

 is well seen in the common Garden Mari- 

 gold, Calendula, in whose calyx, when 

 ripening seed, the naked and barren disk 

 is conspicuous. Othonna, Curt. Mag. 

 t. 306, ?68, Arctotis, Osteospcrmum and 

 Silphium, not rare in gardens, are further 

 examples of this Order, which I believe is 

 constant and founded in nature. We have 

 no British specimens either of it or the 

 following. Filago, at least as far as our 



