378 THE STRUCTURE OF ECONOMIC PLANTS 



They are covered by a finely granular cuticle; and, as the cells 

 develop, stratified layers of material are laid down against the 

 thick outer walls until they nearly fill the cell cavities with a 



int~ 



i int 



,0 int 



i int\ — 



Fig. 191. A, median longisection of anatropous ovule; B, C, and D, progressive stages 

 in development of seed coats. The numbers 1-6 represent corresponding cell layers or their 

 derivatives in the four figures : car, caruncle ; emb s, outline of embryo sac ; end, endosperm ; 

 fun, funiculus; i int, inner integument; mk, micropyle; int, outer integument. (Re- 

 drawn after Tschirch and Oesterle, Anatomischer Atlas der Pharmakognosie und Nahnmgsmittle- 

 kunde, Herm. Tauchnitz.) 



mucilaginous substance that is related to the medicinal properties 

 of the seed. (Fig. 191, D.) 



Haberlandt (9) has described the structure and behavior of this 

 layer when water is gradually imbibed. Each cell is separated 

 from those adjacent by a thin, sharply defined middle lamella 



