DISPERSIOA\ 



299 



employed in ancient warfare to harass the enemy's 

 cavalry. One of these kind of caltrops {Ti-ibuhis 

 terrestris) is widely diiTused, probably on account 

 of the facility with which the fruits are transported 



Caltrops, or fruits of Tribuhis icrrcsiri 



in the wool of animals. They have an elegant, 

 symmetrical, star-like form, and the spines are very 

 sharp and rigid. Another, but less complex, fruit 

 {Pedalmui niurex) has its dispersion provided for in a 

 similar manner. The name of caltrops has also been 



P^^S- 55- — Fruits oi Pcdaliiiiii vutrcx. 



given to one of our indigenous plants, called also "star- 

 thistle," on account of the sharp spines of its woody 

 involucre {Centaurea calcitrapd). More efficient still 

 are the recurved hooks with which some of the 

 spines of fruits are terminated. To a limited extent 



