ON PROTRUSION IN PROTOPLASMIC FILAMENTS. 271 



not, therefore, seem impossible that an elongated filament shouUI 

 crawl or spread itself over the surface of the leaf, its proximal 

 end remaining attached to the gland ; and in this way ammonia 

 might be absorbed and transmitted to the gland, from the dew 

 or rain collected on the leaf. The following observation seems 

 to show that the filaments can adhere to smooth surfaces ; and 

 this faculty, in conjunction with their powers of contraction and 

 extension, would enable them to crawl on the surface of the leaf. 

 A free or unattached filament being in the field of the micro- 

 scope, the preparation was irrigated with methylated spirit. The 

 filament did not float away with the current, but evidently 

 adhered to the under surface of the cover-glass. When the 

 alcohol reached it the filament actually contracted against the 

 force of the current, showing how firmly it was attached to the 

 glass.i 



Schlosing^ has shown that the leaves of the tobacco-plant, 

 when supplied with the vapour of carbonate of ammonia, yield on 

 analysis a greater amount of nitrogen than other plants not thus 

 treated. My father remarks that the vapour may be, perhaps, 

 absorbed by the glandular hairs on the leaves. Dr. Gilbert^ 

 also states that Adolph Mayer has " experimentally shown that 

 plants can take up nitrogen by their leaves from ammonia sup- 

 plied to them in the ambient atmosphere."' There is, therefore, 

 nothing extraordinary in the belief that the leaves of the teasel 

 absorb ammonia from the atmosphere; the novelty is merely 

 in the method of absorption, viz. by protoplasmic filaments. 



It is therefore important to know whether the amount of avail- 

 able ammonia in the atmosphere is sufficient to be an item 

 in the food of the plant. MM. Schlosing and Mayer (as quoted 

 by Dr. Gilbert) appear to believe that the absorbing action 

 " takes place in a very immaterial degree in natural vegetations." 

 This may be from a lack of absorbing organs on the part of the 

 leaves, or from the small quantity of ammonia which is available for 



' Tills observation suggested that the filaments migiit in the adult 

 plant crawl over the dead bodies of the drowned insects, and thus absoil) a 

 strongly nitrogenous nutriment. I therefore cut thin sections of roast 

 meat acrO!>s the fibres, and placed the minute fragments thus obtained 

 round and among tlie glands on a section of a teasel-leaf. But not a 

 single filament applied itself to a piece of meat. I also thought that 

 the filaments might have the power of seizing minute granules floating in 

 the muddy water of the cups. I tried a number of experiments in the 

 hopes of deciding the question. Preparations were irrigated with finely 

 divided carmine suspended in slightly ammoniacal fluid, but no particles 

 were ever seized by the filaments. 



- ' Insectivorous Plants,' p. 353 ; for the original see ' Comptes rendus,' 

 June 15th, 1874. 



3 Address delivered at South Kensington at the Science Conferences, 

 1876. 



