126 TARAXACUM, ARTEMISIA, DIPSACE^E. [CH. 



they rapidly withdrew themselves 2 3 mm., and then 

 more slowly, 4 6 mm. 



Taraxacum (the Dandelion). In T. offidnale the 

 heads consist of 100 200 florets. In fine weather 

 they stand open, but at night and during rain they 

 close completely. The two lobes of the stigma 

 gradually curl over, so that if the visits of insects 

 are delayed the flower always fertilises itself. The 

 honey, however, is so abundant, and rises therefore 

 so high in the floret, that it is very accessible to 

 insects, no less than 93 species of which have been 

 observed by Miiller to visit this plant. The bright- 

 ness of its colour, the quantity of its honey, the habit 

 of closing in unfavourable weather, and the power of 

 self-fertilization, go far to explain the great abundance 

 of the Dandelion. 



The genus Artemisia has minute greenish florets, 

 and is said to be wind-fertilised. 



This order is the subject of an admirable memoir 

 by Hildebrand (Ueber die Geschlechtsverhaltnisse bei 

 den Compositen). 



DIPSACE^E. 



There are two British genera belonging to this 

 order ; Dipsacus (the Teasel) and Scabiosa. The so- 

 called flower is a compound flower head, as in the 

 Compositae, from which, however, this group may be at 

 once distinguished by possessing free anthers. .Each 

 floret, moreover, is inserted in a small "involucel." 



Dipsacus is a proterandrous genus. The pistil 

 terminates in two lobes, the upper surfaces of which 

 constitute the stigma. As, however, in consequence 



