236 SHEPHERD'S PURSE. 



From this point the development of the embryo may be 

 traced with greater or less particularity, by examining 

 ovules in various stages of advancement, until the following 

 condition is seen in seeds from a young pod : 

 v. The pro-embryo has disappeared. 

 vi. The embryo nearly fills the embryo sac, the 

 cotyledons beginning almost exactly at the 

 bend, 

 vii. Make drawings illustrating this development. 



E. THE FRUIT. Make a tranverse section through as 

 old a fruit as possible, clear with potash, and note 



1. The nature of the epidermis, mesophyll, fibro-vascular 

 bundles, placentae and partition, compared with that 

 studied in the ovary. 



2. The seed. In transverse sections of seeds note 



a. The testa, its color and structure. 



b. The thin-walled tissue filled with food material. 



c. The cotyledons, the nature of their tissues as com- 

 pared with those of the leaf. 



d. The caulicle, its structure and tissues as com- 

 pared with those of the stem. Draw. 



e. Draw a complete section of the seed, filling in 

 enough of the tissues to indicate their character. 



ANNOTATIONS. 



Capsella very well presents in a compact form the 

 salient features of a dicotyledon. The paired cotyle- 

 dons, net-veined leaves, four-parted flowers, and con- 

 tinuous fibro-vascular zone of the stem, all mark it as a 

 member of this highest group. 



