DIGESTION 
258 
(fig. 122) and the secreting structures of the leaves of Dioncwa 
and other plants, as well as the similar bodies which occur 
ic. 121.—Srotion trHroveH ExternaL REcIon or GraIn 
or BaRLEY. 
p, pericarp of fruit; ¢, testa of seed; al, layer of cells 
containing aleurone grains; .am, cells of endosperm; 
n, nucleus. (After Strasburger.) 
in the lining of the pitcher of Nepenthes, must be regarded 
ag actual glands, comparable to those 
of the alimentary canal of the animal 
body, though less complex in structure. 
Glandular hairs, which consist of a. few 
cells situated on a stalk, are found in 
great numbers on other plants, especi- 
ally some species of Saaifraga. 
There are many of these enzymes 
present in different plants, the function 
of some of which is still not understood. 
Many, however, have been investigated 
with some completeness. They are 
usually classified according to the mate- 
rials on which they work. We may 
describe here four groups, the members 
Fic. 122.—GLanpuLar 
ApEx oF A TENTACLE 
or Drosera. 
of which take part in the digestion of reserve materials, 
as well as in the processes of external digestion. These 
