CATAPULT FRUITS. 



841 



rocking to and fro, the fruits are thrown out from between the elastic tips of the 

 scales and describe an open curve before they reach the ground. A third group of 

 Composites, which may be represented by Centaurea Pseudophrygia and C. steno- 

 lepis, exhibits the following arrangement : The receptacle is destitute of palese, but 

 the involucral scales form a sort of basket at the bottom of which are the fruits. 

 In damp weather the tips of the bract-scales close tightly together, and the short 

 bristles of the pappus crowning each fruit are applied closely to one another. In 

 warm, dry weather especially, under the influence of a dry wind and sunshine, the 

 scales part asunder and the basket stands wide open. At the same time the hairs 



Fig. 460. —Catapult fruits. 



' and 2 Salvia verticillata. s, < ' and » Teucrium Uvganceum. ' aiid » Teucrium flavum. 

 11 Polygonum Virginicum. i, ^ and lo nat. size ; the others magnified. 



9 Monarda Jistulosa. lo and 



of the pappus bristle up, and in so doing raise the fruits to the open mouth of the 

 basket. If the peduncle supporting the capitulum is now set in motion, the fruits 

 are tossed out like shuttle-cocks. The bristly pappus-hairs are not in this case 

 organs of flight ; they are short and stifi", and, besides raising the fruits, serve also 

 to determine the direction of their fall. Balistic apparatus very similar to that 

 just described is also found in several Iridacece, Liliacece, Caryophyllacece, Primu- 

 lacecB, and Scrophulariacece, only in them the erect, resilient stem does not bear a 

 fruit-capitulum but a capsule, and the ejected particles are not fruits but seeds, 

 The seeds are comparatively large and heavy, and are destitute of membranous or 

 hairy appendages. In all these cases the capsule is situated with its oriflce upwards 

 and only opens in dry weather. As its cavity is very deep, no ejection of the seeds 

 ensues except w;hen the resilient stalk which carries it sways somewhat violently 

 to and fro. 



