32 
Gardiner and I to. — On Mucilage-cells 
III. Special Observations. 
(a.) Blechnum occidentale, L. 
This species was used in preference to Blechnum brasiliense, 
Desv., both because it demonstrated more clearly the minute 
histology of the gland-cells, and also on account of its freely 
branching habit which ensures the production of a sufficient 
supply of growing points. The stem is provided with 
numerous paleae, and both on the structure and on the young 
leaves there are numerous mucilage and resin-secreting gland- 
cells (Figs, i, 2, and 3). In each of the paleae the apex is 
terminated by a single mucilage-gland borne on a long stalk 
which is filamentous and multicellular. This stalked gland is 
developed at a very early stage in the history of the scale 
(Fig. 4), and by the time the rest of the glands are produced 
along the scale-edge, and have become functional, the apical 
cell has perished and its contents have usually quite dis- 
appeared (Fig. 1). With the exception of this terminal 
cell which always secretes mucilage, the remaining glands 
may be either entirely mucilaginous or entirely resinous in 
character, or in many cases both forms may occur. The resin- 
glands are usually simple and sessile, and the secretion appears 
outside the cell-wall, collecting beneath the cuticle which 
becomes raised up like a blister, as in so many resin and 
oil-producing hairs (Fig. 31). The mucilage-glands are 
usually stalked and the secreting cell is large and swollen, but 
the secretion escapes in this case only on the rupture of the 
cell-membrane (Fig. 27). The foregoing remarks upon the 
anatomy of the paleae-hairs will equally apply to those of the 
leaves. Both mucilage and resin -glands occur distributed 
over the surface. The mucilage-hairs are especially localised 
in relation to the vascular bundles, and rows of them arise 
from those epidermal cells which are placed immediately 
above the main vascular trunks. In like manner the resin- 
hairs are met with in greatest number along the edge of the 
young leaves. Having teased out and mounted a preparation 
