Ill 



545. FOR EXAMPLE, the oak-acorn is a fruit with but one cell and one seed, al- 

 though its ovary had three cells and six ovules 1 This singular change is due to the 

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

 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, Section of the ovary of an acorn, 3-ceIled, 6-ovuled. 420, Section of ovary of Birch, 

 2-ce!led, 2-o vuled. 419, Vertical section of the same in fruit. 422. Pericarp of Mignionette open 

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

 fleshy pericarp. 



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

 the fruit becomes 1-celled and 1-seeded. 



546. Ox THE OTHER HAND the cells are sometimes multiplied in the fruit by the 

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

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

 partitions formed between the seeds. 



426 427 



423 425 424 423 



Capsule, 42T, of Scrophularia, 2-celled ; 423, of Datura Stramonium ; 425, of Iris ; 426, show- 

 Ing its mode of dehiscenco (loculicidal) ; 424, of Colchicum, 3-celled. 42S, Eegma, ripe fruit of 

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



PERICARP. 



The fruit consists of the pericarp and the seed. 



547. THE PERICARP (rrept, 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 



