248 



PLANT ORGANS OR PARTS OF PLANTS. 



Beneath this a zone of colorless cells filled with aleurone 

 grains and oil, and finally a many rowed layer of empty 

 compressed cells. 



VIII 



.4Y 



Fig. 72. — White Mustard (Sinapis Alba). 

 I, Part of testa: Gr, large cells; Ps, palisade cells; pg, pigment 

 layer; Al, aleurone layer; S, hyaline layer. II, Isolated cells of sclereid 

 layer. Ill, Sclereid layer seen from surface. IV, Aleurone layer. V, 

 Epidermis. VI, Large cells from above. VII, Fragments of large cells 

 in powder. VIII, Tissue from cotyledon (Vogl). 



The cotyledons consist of a regular thin-walled par- 

 enchymatic tissue whose outer layers are thicker walled 

 and smaller. 



