Cuar. 1Y. VITACER. 147 
tip; this was also observed (p.71) by Mohl. The discs 
consist of enlarged cells, with smooth projecting hemi- 
spherical 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. 
Immersion in sulphuric ether for 24 hrs. loosened them 
much, but warmed essential oils (I tried oil of thyme 
and peppermint) completely released every particle of 
stone in the course of a few hours. This seems to prove 
that some resinous cement is secreted. The quantity, 
however, must be small; for when a plant ascended 
a thinly whitewashed wall, the discs adhered firmly to 
the whitewash; but as the cement never penetrated 
the thin layer, they were easily withdrawn, together 
with little scales of the whitewash. It must not be 
supposed that the attachment is effected exclusively 
by the cement ; for the cellular outgrowth completely 
envelopes every minute and irregular projection, and 
insinuates itself into every crevice. 
A tendril which has not become attached to any 
body, does not contract spirally; and in course of a 
