FRi'ir 



riic woody pear is the hard fruit of a New 

 llolland plant which spHts open to release the 

 seeds. The horse-chestnut is a conspicuous instance 

 of a dehiscin<^ fruit, the rou<;h jjrickly j^art is the 

 pericarp, and when the fruit is mature this splits 

 open and allows the two large chestnuts (seeds) 

 to escape. In the sweet- 

 chestnut we get an alto- 

 L^ether different structure. 

 If we [jick up one of its spin}' 

 burrs, we hold in our hand 

 what is called in botan\' an 

 involucre (from involucruni, 

 a cover), that is, a number 

 of bracts which have grown 

 together and formed an 

 outer case to the fruit. The 

 acorn-cuj) is an inxolucre, and 

 we may find other good examples in composite 

 flowers and those of the umbellifera;. The small 

 green whor! in which a daisy-flower is set is, there- 

 fore, not a cal\x, but an involucre consisting of 

 minute bracts grown together. The true fruit of 

 the sweet-chestnut is enclosed in a mass of spin)' 



I'OIM'Y CAl'Sri.K. 



