240 PLANT ORGANS OR PARTS OF PLANTS. 



SEEDS. 



Seeds possess few universal characters. In general the 

 tissues to be distinguished microscopically are the cells of 

 the seed coat, or testa; those of the nucleus of the young 

 plant, and those of the cotyledons. The seed coat differs 

 greatly in the different seeds. In general, however, it is 

 composed of parenchymatic cells with greatly thickened 

 cell walls. The thickness of the cell walls differs in every 

 seed, but most of the seeds of the Pharmacopoeia have 

 stone cells in the seed coat. The tissues of the cotyledons 

 are usually thin- walled and parenchymatic. Occasion- 

 ally very delicate spiral vessels may be found in the 

 cotyledons. Aleurone grains and starch grains are im- 

 portant features in seed structures. One or the other, 

 and frequently both, are found in seeds. 



AMYGDALUS DULCIS. SWEET ALMOND. 



The seed of Amygdalus communis, L., a plant originally 

 found in Asia about the region of the Caspian Sea, now 

 quite widely spread by cultivation in the milder climates 

 of the world. Southern Italy, Spain and Greece, and the 

 northern countries of Africa are the regions more com- 

 mercially active. 



Description. — Elongated, thin; average size 2.5 cm. 

 long and i cm. broad, 0.5 cm. thick. 



Commonly two forms are found, those with the hard 

 shell and the paper-shelled. In the hard shell the outer 

 pericarp wall is thick and plentifully provided with stone 

 cells. In the paper-shelled this outer pericarp layer is 

 more fibrous and thinner. The inner walls of the shell 

 are alike in the two ; hard, made up of compact smooth 

 layers of stone cells ; between the two layers a more or less 

 corky tissue is to be found, thickly interwoven with 

 fibro-vascular bundles. Some stone cells may be found 

 interspersed. 



