72 



ELEMENTS OF /tPPLIED MICROSCOPY. 



3. The Microscopic Structure of Coffee. — ^The coffee- 

 bean is the seed of Coffea arabica, a small tropical tree of 

 the family Rubiaceae, two of the semi-ellipsoidal beans 

 lying base to base in each of its berries. The beans are 

 brought into the market generally roasted, either in their 

 original form or ground, and although adulteration ' is 

 most easy in the second condition, artificially modelled 

 beans of foreign material are not unknown. 



The true coffee-bean is made of thick-walled cells, 

 approximately isodiametric, and packed with a finely 



Fig. 



29. — Microscopic STRtrcruRE of Coffee. 

 240 diameters. 



(After Schimper.) 



granular material containing minute oil-drops. The 

 cells of the inner part are very characteristic, showing 

 knotty thickenings of their walls, as indicated at B in 

 'Fig. 29. More peripheral cells (C) are smaller and lack 

 these swellings, while at the extreme outside of the bean 

 is the so-called silverskin, a thin glistening layer contain- 

 ing peculiar fusiform cells with wide walls pierced by 



