428 



FERTILIZATION AND FORMATION OF FRUIT IN PHANEROGAMS. 



peculiar in that the flesh is contributed not only by the pericarp proper (fruit- wall),- 

 but also by the outmost layer of the seed-coat. It is the inner layer of the seed- 

 coat which here gives rise to the stone. 



When the outer part of the pericarp is fleshy, and the inner part which imme- 

 diately invests the seeds stony, the fruit is called a Drupe or stone-fruit. The 



Fig. 323.— Winged Fruits. 



1 Cluster of fruits of the Ash {Fmxiims excelsior). 2 A single fruit artificially opened, » Seed of Fraximis excelsior. * The 

 same seed in longitudinal section. ' Fruit of Banisteria. « Fruit of Angelica sylcestris. ' Fruit of Ailanthus glanaulosa, 

 the central, seed-containing portion seen In section. (Partly after Baillon.) 



majority of drupes, e.g. the Sloe (Prunus spinosa), and Cherry (Prunus aviuTn), 

 contain only a single stone and seed. That of the Buckthorn (Rhamnus) contains 

 two stones, each of which contains a seed, whilst that of the Elder (Samh-itcus 

 nigra), usually described as a berry, is in reality a drupe containing from 2-4 stones 

 each with one seed. 



In a very large number of fruits the pericarp is entirely dry. These dry fruits 



