Chap. 1\'. VITACE^. 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 the thin layer, they were easily withdrawn, together 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 



