CHAP, v.] RELATIONSHIP AMONGST PLANTS. 169 



clearly indicated externally by grooves along the ovary 

 corresponding to the junction of the margins of the com- 

 ponent carpels, as in the tiger-lily, whereas in other 

 cases, as that of the hazel-nut, the " shell/' which is the 

 fruit consisting of two carpels, shows no external evidence 

 as to number of carpels forming it at maturity, and in 

 addition has become hard and woody, thus departing 

 from the leaf-like carpel of the pea. The object of 

 becoming hard and woody is for the purpose of protect- 

 ing the inclosed seed, popularly known as the " kernel." 



Fig. 51. Fruit of the peach 

 (Persica vulgaris), cut open and 

 showing the structure of the fruit, 

 which includes the outermost 

 skin, the succulent portion, and 

 also the " stone," the seed being 

 the portion usually called the 

 "kernel." (Natural size. ) 



Speaking of the " shell " of the hazel-nut as a fruit may 

 possibly cause some surprise, but the popular conception 

 of a fruit as being that of something good to eat, is not 

 in accordance with the botanical definition ; according 

 to the latter, the carpels at maturity constitute the fruit, 

 whatever their consistency and properties may be, and 

 the earliest function of the fruit in the ovary condition 

 is that of protecting the young ovules, and all subse- 

 quent changes in its condition are connected with either 

 continued protection of the seed, as in the case of the 

 hazel-nut, already mentioned, the walnut, cocoa-nut, etc. ; 



