When they were developed in contact with a ball of tow,
the fibres were separately enveloped, but not in so effective a
manner as by B. capreolata. Discs are never developed, as far as I
have seen, without the stimulus of at least temporary contact with
some object. {32} They are generally first formed on one side of the
curved tip, the whole of which often becomes so much changed in
appearance, that a line of the original green tissue can be traced
only along the concave surface. When, however, a tendril has clasped
a cylindrical stick, an irregular rim or disc is sometimes formed
along the inner surface at some little distance from the curved tip;
this was also observed (p. 71) by Mohl. The discs consist of
enlarged cells, with smooth projecting hemispherical surfaces,
coloured red; they are at first gorged with fluid (see section given
by Mohl, p. 70), but ultimately become woody.
As the discs soon adhere firmly to such smooth surfaces as planed or
painted wood, or to the polished leaf of the ivy, this alone renders
it probable that some cement is secreted, as has been asserted to be
the case (quoted by Mohl, p. 71) by Malpighi. I removed a number of
discs formed during the previous year from a stuccoed wall, and left
them during many hours, in warm water, diluted acetic acid and
alcohol; but the attached grains of silex were not loosened.
Pages:
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190