74 PHILOSOPHICAL NOTES ON 



S. pulcher. Indeed, one can imagine the whole corymb of small 

 capitula transformed through this ' process into one large 

 capitulum. 



Senecio Doria, as I saw it at Kew, appeared to me as if it 

 might be considered a link between the non-ligulate composites, 

 that is, those without ray florets, such as groundsel, and Cacalia, 

 and those composites which are furnished with a ray. The 

 common groundsel itself, according to Syme, has two varieties, 

 one with and one loithout the ray florets. 



Nothing, perhaps, would be more interesting than to gather all, 

 or as many as possible, of the British composite plants and study 

 them from an evolutionary point of view. 



No doubt in fusing, some of the ray florets may be suppressed, 

 or squeezed out of existence, for the ray of two fused heads has 

 often little more ray florets' than the one head, although those of 

 the disk may be almost doubled, or there may be two rows of ray 

 florets, as I have seen in several duplicated capitula of Erigeron. 



It may be naturally asked, " How is an elongated disk of two 

 fused Pyrethrums, with a line for its dimple, changed into a 

 circular disk, with a round dimple in its centre, and without any 

 trace of its having been the result of a fusion of two or more 

 heads ? 



The phenomenon of conversion from the oval to the circular 

 form would appear somewhat puzzling ; but a little consideration 

 will show us that the force which effects the conversion is of a 

 polar nature, or the same as that of gravitation. 



Of course the individual oval head is never changed into a 

 circular head. It produces seeds which result in flower heads, 

 which are more and more circular each generation, until the 

 ovality is entirely extinguished. 



The circularity is shaped by polar force, or force of gravity, 

 while the head is still in a " fluid " cellular stage. The same force 

 which makes a liquid suspended in the air, or in space, take the 

 globular form, will make the unformed oval flower head, take on 

 by degrees and through several generations the circular and 

 perfect shape. The parts, when free to move, aggregate round a 

 common centre, which is afterwards indicated by the central 

 dimple. That is, the disk and ray in composite flowers, when 

 they are still cellular and unformed, tend to arrange themselves 

 round a common centre, and thus produce a circular capitulum. 



