ON PROTRUSION OF PROTOPLASMIC FILAMENTS. 251 



pressure, so that it somewhat resembles in appearance a heap of 

 soap-bubbles, as shown in fig. 5. I may remind the reader that 

 when a colourless blood- corpuscle dies it swells up into a transpa- 

 rent sphere, owing to the imbibition of water,i and I believe that the 

 formation of the soap-bubble mass is due to the protoplasm of the 

 filament imbibing water at a number of diff'erentpoints.^ This soap- 

 bubble appearance is not specially connected with death by acetic 

 acid; it appears to be a result of any kind of death, and may be seen 

 where the filament has been killed by other reagents (such as ^ 

 per cent, solution of chloride of gold) or by heat. On the other 

 hand it is not the invariable accompaniment of any kind of 

 death, simple balloon-like masses being often produced by the 

 swelling of the protoplasm in a single mass. 



Sulphuric acid. — By irrigating with 2 per cent, solution of 

 sulphuric acid contraction was several times produced. Weaker 

 solutions were not tried. 



Hydrochlonc acid. — As my father found this acid not poison- 

 ous to Drosera, a dilute solution (2 per cent.) was tried with the 

 teasel. Contrary to my expectations, it proved poisonous, 

 always causing contraction and death of the filament. 



Boracic acid. — This acid is not poisonous in a weak solution. 

 Several long and delicate filaments were found protruded after 

 being immersed all night in '2 per cent, solution, and they con- 

 tracted at once with dilute acetic acid. In this case the teasel 

 agrees with Drosera, as boracic acid is not poisonous to the latter.^ 



Citric acid. — This acid is not poisonous to Drosera,* and is so 

 to the teasel, but I cannot speak decisively as to how poisonous 

 it is. A solution of 1 per cent, rapidly causes contraction. A 

 solution of '5 per cent, usually produces contraction after a time, 

 and also kills the glands. But two filaments withstood a solu- 

 tion of this strength for between seventeen and eighteen hours ; 

 two others were not made to contract by five hours'* immersion in 

 the same solution. 



Osmic acid. — The action of this highly poisonous acid has 

 surprised me much. As is well known, its usual efl'ect on 

 protoplasm is to kill it instantaneously without altering its 

 appearance. This is not the case with the filaments of the teasel, 

 at least with weak solutions of the acid, which act like acetic or 

 sulphuric acids, but not so vigorously, and sometimes not com- 

 pletely. I record in my notes that on irrigating with \ per cent, 

 solution of osmic acid a whip-like filament ''contracted into a 

 barred and knobbed cylinder." I then irrigated with water, and 



* 'Handbook for the Physiological Laboratory/ p. 12. 

 ' Perhaps this may be connected with the filament's power of contracting 

 at a number of equidistant points. 

 ' ' Insectivorous Plants/ p. 191. ■• Ditto, p. 194. 



