CHAPTER VIII 



STORAGE TISSUE 



Most drug plants contain storage products because they 

 are collected at a period of the year when the plant is storing, 

 or has stored, reserve products. These products are stored 

 in a number of characteristic ways and in different types of 

 tissue. 



The most important of the different types of storage tissue 

 that occurs in plants are the storage cells, the storage cavities, 

 and the storage walls. 



STORAGE CELLS 



Several different types of cells function as storage tissue. 

 These cells, which are given in the order of their importance, 

 are parenchyma, crystal cells, medullary rays, stone cells, wood 

 fibres, bast fibres, and epidermal and hypodermal cells. 



CORTICAL PARENCHYMA 



Cortical parenchyma of biennial rhizomes, bulbs, roots, 

 and the parenchyma of the endosperm of seeds store most of 

 the reserve economic food products of the higher plants. 



Pith parenchyma of sarsaparilla root (Plate 65, Fig. 4) and 

 the pith parenchyma of the rhizome of memspermun, like the 

 pith parenchyma of most plants, function as storage cells. 



WOOD PARENCHYMA 



Wood parenchyma, particularly of the older wood, function 

 as storage tissue. The wood parenchyma of quassia, like the 

 wood parenchyma of most woods, contain stored products. In 

 some cases the wood parenchyma contain starch, in others crys- 

 tals, and in others coloring matter, etc. 



In many plants, however, the parenchyma cells contain 

 crystals. The parenchyma cells of rhubarb contain rosette 



173 



