COMPOSITE 



233 



in these outer flowers the branches of the pistil do not 

 possess the terminal brush of hairs, which in the absence 

 of pollen would be useless. 



When the fruits are ripe the involucres press strongly 

 inwards. If the fruits are removed it will be found that 

 the bracts quickly close in. On the other hand, when 

 it is dry they open out and thus allow the fruits to 

 escape. This is well seen in Centaurea. The dispersal 



Fig. 150. 



Kg. 151. 



Fig. 152. 



FiciS. 150-152. — Ohrysanthemum Parthenium. Successive stages in the life of the 

 flower, ffl, anthers ; st, stigmas. 



of the fruits has been specially studied by Hilde- 

 brand.^ In some there is no special provision, but 

 they are small and easily carried by the wind. In 

 many cases they are surmounted by a ring of simple or 

 plumose hairs, or flat scales. In Dahlia the floral bracts 

 or palese are long, membranous, and attached to the fruit, 

 thus forming a wing ; in Melampodium the corolla is 

 persistent, and serves the same purpose. In other cases 

 (Bidens, Lappa) they are covered with hooks, or are sticky, 

 and attach themselves to animals. In one genus (Wulffia) 



^ " Ueber die Verbreitungsmittel der Compositen-friichte," Bot. Zeit. .xxx. (1872). 



