418 West. — On the S trite here and Development of 
a general rule it was noticed that those associated with a vascular bundle 
are relatively much narrower than those which occur in the ground-tissue. 
They invariably possess thin cellulose walls even when they are 
embedded in the fibrous zone of the petiole (Text-fig. 8). 
Text-fig. g. Tannin-cells in the petiole of 
Angiopteris evecta , Hoffm. The large tannin¬ 
cell x is crushed by the surrounding parenchyma. 
X 220 . 
Text-fig. io. Tannin-duct from 
the petiole of Angiopteris evecta , 
Hoffm. The contents of the duct 
are not shown, x 220. 
Text-fig. ii. Series of tannin-cells from 
the stem of Danaea nodosa, Sm. x 150. 
They not infrequently occur associated together in regular series 
of superposed cells, e. g. in the stem, root, and petiole of Angiopteris evecta 
(Text-fig. 10 ; Fig. 5, t.c.) ; in the root of Danaea alata , Danaea nodosa , and 
