98 MR. J. H. BURRAGE ON THE 
by means of a mucilaginous secretion, such as described in the 
case of Ampelopsis* and of many adhesive roots of Aroids, 
Ficus sp. &e.t 
This seeretion takes place only at early contact, when it pro- 
trudes from the apices of the hairs and can be stained pink by 
the action of corallin. The hairs increase in length, forcing 
their way into crevices, and apparently eating into the substance 
of the support, probably by means of a solvent secretion. The 
walls of the hairs become considerably thickened, the protoplasm 
at the same time being gradually diminished, possibly being 
used up in forming the extra thickening of the wall. The cellu- 
lose wall is now gradually cuticularized, the euticularization 
increasing as the dise grows older. The thickening of the walls 
gives considerable strength to the hairs, which bind the braneh 
close up to the support, the disc adhering with considerable 
tenacity. If the latter be torn away, small disorganized par- 
ticles of the support are found embedded among the mass of 
hairs. 
Secondary changes in the Disc.— The disc does not remain 
long in this condition, as changes soon occur which modify the 
nature of its structure. The walls of the cells immediately 
below the hairs become gradually suberized, down to within 
three or four cell-layers of the vascular tissue. In spite of this, 
the peripheral cells retain their protoplasmie contents for some 
time, eventually losing them, but retaining their original contour 
by reason of the thickened walls. 
A little later there appears in the cells below the corky layers, 
and just outside the plate of tracheides, a cambium (Pl. 5. fig. 6,0), 
which forms a definite periderm of three or four rows of cells. 
This completely isolates the outer part of the dise from the 
vascular tissue. 
At this stage the disc is made up of the following tissues :— 
(1) somewhat collapsed, empty hairs, with thickened walls, below 
which are (2) several irregular layers of corky cells, in which 
raphides frequently occur. Still more internally lies (3) a re 
gular periderm, springing from a phellogen which is separate 
by (4) three or four layers of small-celled parenchyma from 
(5) the plate of tracheides. The large parenchymatous cells below 
* Darwin's ‘Climbing Plants,’ p. 147. 
t F. A. F. C. Went, * Ueber Haft- und Naerh-Wurzeln bie Kletterpflanze? 
und Epiphyten.” Ann. du Jardin bot. de Buitenzorg, vol. xii. (1894). 
