TENDIUL-BEAItERS. 85 



little disks or cushions, which adhere firmly to the surface. In 

 one case these tips became slightly swollen in 38 h. after coming 

 into contact with a brick ; in another case they were considerably 

 swollen in 18 h., and in an additional 21 h. they were firmly at- 

 tached to a smooth board ; and lastly, the tips of a younger ten- 

 dril not only swelled but became attached to a stuccoed wall in 

 42 h. These adhesive disks resemble, except in colour and in 

 being larger, those of Bignonia capreolata. When they were de- 

 veloped in contact with a ball of tow, fibres were separately enve- 

 loped, but not in so effective a manner as with B. capreolata. 

 Disks are never developed, as far as I have seen, without the 

 stimulus of at least temporary contact with some object. They 

 are generally first formed on one side of the curved tip, the whole 

 of which often becomes so much changed, that aline of green unal- 

 tered tissue can be traced only along the concave surface. When, 

 however, a tendril has clasped a cylindrical stick, an irregular 

 rim or disk is formed along the inner surface at some little distance 

 from the curved tip ; this was also observed (S. 71) by Mohl. 

 The disks consist of enlarged cells, with smooth projecting hemi- 

 spherical surfaces, coloured red, and at first gorged with fluid (see 

 section given by Mohl, S. 70), but they ultimately become woody. 

 As the disks can almost immediately adhere firmly to such 

 smooth surfaces as planed and painted wood, or to the polished 

 leaf of the ivy, this alone would render it probable that some 

 cement is secreted, as has been asserted to be the case (quoted by 

 Mohl, S. 11) by Malpighi. I removed a number of disks formed 

 during the previous year from a stuccoed wall, and placed them in 

 warm water, diluted acetic acid and alcohol during many hours; 

 but the attached grains of silex were not loosened : immersion in 

 sulphuric ether for 24 h. much loosened them ; but warmed essen- 

 tial oils (I tried oil of thyme and peppermint) in the course of a 

 few hours completely released every atom of stone. This seems 

 to prove that some resinous cement is secreted; the quantity 

 secreted, however, must be small ; for when a plant ascended a 

 thinly whitewashed wall, the disks adhered firmly to the white- 

 wash ; but as the cement never penetrated the thin layer, they 

 were easily withdrawn, together with little scales of the white- 

 wash. It must not be supposed that the attachment is by any 

 means exclusively effected by the cement; for the cellular out- 

 growth completely envelopes every minute and irregular projec- 

 tion, and insinuates itself into every crevice. 



A tendril which has not become attached to any body, does not 



