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 
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