PERICARP. 



Ill 



545. !P0R EXAMPLE, the oak-aoom is a fruit with but one cell and one Beed, al- 

 though its ovajy hadiihree cells and six ovules ! This singular change is due to tl-"> 

 non-development of five of its ovules, while the sixth grew the more rapidly, obh 

 erated the dissepiments by pressing them to the wall, and 

 filled the whole space itself. Similar changes characterize 

 the chestnut, hazelnut, and that whole order. The ovary of 



418 



418, Section of the ovary of .in acorn, 8-celled, 6-ovuliid. 420, Section of ovary of Birch, 

 2-celle(l, 2-ovule(]. 419, Vertical section ofthe same in fruit. 422, Pericarp of Mignionette open 

 soon after ilowering, 421, Naked seed of Taxus Canadensis, surrounded, not covered by the 

 fleshy pericarp. 



the birch is 2-oelled, 2-ovuled ; but by the suppression of one cell with its ovule, 

 the fruit becomes l-celled and 1-seeded. 



546. On the other hand the cells arc sometimes multiplied in the fruit by the 

 formation of false partitions. Tlius the pod of thorn-apple (Datura) becomes 4-celled 

 fi-om a 2-celled ovary, and the longer pods of some leguminous plants have cross- 

 partitions formed between the seeds. 



42T 



428 425 424 423 



Capsule, 42T, of Sorophularia, 2-celled ; 423, of Datura Stramonium ; 425, of Iris; 426, shoTV- 

 Ing its mode of dehiscence (looulicidal) ; 424, of Colehicum, S-oelled. 423, Eegma, ripe fruit of 

 Geranium, the carpels (cocci) separating from the axis and bending upwards on the elastic styles. 



PEEICAEP. 



The fruit consists of the pericarp and the seed. 



547. The pericarp (rrepi, around) is the envelope of the seeds, con- 

 sisting of the carpels and whatever other parts they may be combined 

 ■with. It varies greatly in texture and substance when mature, being 



