ie ie! ae 

cells which surrounds the 
stele and contains numer- 
ous starch grains, from 
which circumstance its 
name is derived (Figs. 
114,116). Frequently it 
is most easily distinguish- 
able from the surround- 
ing tissue by the presence 
of these starch grains. 
The part of the cortex 
situated between the epi- 
dermis and the starch 
sheath is usually divided 
into two regions, an in- 
ner zone of parenchyma 
and an outer zone of 
collenchyma cells (igs. 
113-115). 
Parenchyma. ‘he pa- 
renchyma cells of the 
cortex have the general 
structure and functions 
characteristic of paren- 
chymatous cells (I igs. 
113-115). Such cells are 
not highly specialized in 
structure for the perform- 
ance of any particular 
function, but may be re- 
garded as generalized 
cells which carry on to 
a limited extent all the 
usual functions of cells. 
(PES PEM. 5 - ID 

Fic. 114. Cross section of a portion of stem 
of castor-oil plant (Ricinus communis), show- 
ing a vascular bundle and the tissues around 
and external to it . 
e, epidermis ; c, collenchyma ; pc, parenchyma 
of cortex ; st, starch sheath ; sc, sclerenchyma 
of pericycle; pp, parenchyma of pericycle; 
p, phloém; ca, cambium; v, xylem vessel ; 
yr, pith ray. (x 180) 
Parenchyma cells are ordinarily regular in shape, have com- 
paratively thin walls, and are not greatly elongated in any 
