116 PHARMACEUTICAL BOTANY 
permanent tissues and left with the latter as the apical meristem 
advances in growth. They are found just above or below the 
nodes of many stems and at the bases of some leaves, especially 
those of monocotyls. 
LaTERAL MERIsTEMS are those which occur lateral in an 
organ, as the cambium and cork cambium. 
PARENCHYMA 
PARENCHYMA or FUNDAMENTAL TIssuE is the soft, primitive 
tissue of plants, consisting of cells nearly. equal in length, breadth 
and thickness (isodiametric) with usually thin, cellulose cell 
walls enclosing cytoplasm and a nucleus and frequently sub- 
stances of a non-protoplasmic nature. It is capable of cell 
division after maturity. There are four. generally recognized 
types of parenchyma, viz.: 
OrDINARY PaRENCHYMA (Sorr GrounpD ‘TissuE, FUNDA- 
MENTAL TissuE).—Next to the meristem this is the least modified 
of all plant tissues. It is generally composed of thin-walled 
cells, commonly polyhedral or spheroidal in form and often of 
approximately the same length, breadth, and thickness (iso- 
diametric); the cell walls are composed of cellulose which is 
usually unmodified. Intercellular air-spaces occur in the angles 
of adjoining cells. Occasionally the outline of the cells is star- 
shaped or stellate, as in the stems of Wood Rush or Pickerel 
Weed or the cells may be several times as long as wide, as in the 
stems of Geranium, etc. Moreover, markings may occur on 
the walls. These may be of the nature of pores, as in the 
parenchyma cells of the pith of the Elder or Sassafras, annular 
thickenings, as in the Mistletoe, or spiral thickenings, as in 
certain Orchids. Protoplasm and a nucleus are always present 
as well as colorless plastids, but in old cells are only seen as a 
thin layer pushed up against the cell wall. Ordinary Paren- 
chyma may be seen composing the soft tissues of roots, stems, 
and barks. (See Fig. 69.) 
ASSIMILATION PARENCHYMA (CHLOROPHYLL PARENCHYMA, 
CHLORENCHYMA). This form of parenchyma tissue is found in 
foliage leaves, floral leaves, in the outer region of young green ) 
stems and fruits. Its cells are thin-walled and vary in shape from 
