Chap. II. INFLECTION INDIRECTLY CAUSED. 27 



Accordingly measured lengths of a narrow strip of 

 blotting paper, of fine cotton-tliread, and of a woman's 

 hair, were carefully weighed for me by Mt. Trenham 

 Reeks, in an excellent balance, in the laboratory in 

 Jermyn Street. Short bits of the paper, thread, and 

 hair were then cut off and measured by a micrometer, 

 so that their weights could be easily calculated. The 

 bits were placed on the viscid secretion surrounding the 

 glands of the exterior tentacles, with the precautions 

 already stated, and I am certain that the gland itself 

 was never touched ; nor indeed would a single touch 

 have produced any effect. A bit of the blotting-paper, 

 weighing ^-^ of a grain, was placed so as to rest on 

 three glands together, and all three tentacles slowly 

 curved inwards; each gland, therefore, supposing the 

 weight to be distributed equally, could have been 

 pressed on by only -nnrT of a grain, or -0464 of a* milli- 

 gramme. Five nearly equal bits of cotton-thread were 

 tried, and all acted. The shortest of these was -3^ of 

 an inch in length, and weighed g ^\^ ^ of a grain. The 

 tentacle in this case was considerably inflected in 

 1 hr. 30 m., and the bit of thread was carried to the 

 centre of the leaf in 1 hr. 40 m. Again, two particles 

 of the thinner end of a woman's hair, one of these 

 being -j-^f-o of an inch in length, and weighing xf^Itt o^ 

 a grain, the other -i%-o of an inch in length, and weigh- 

 ing of course a little more, were placed on two glands on 

 opposite sides of the same leaf, and these two tentacles 

 were inflected halfway towards the centre in 1 hr. 10m.; 

 all the many other tentacles round the same leaf re- 

 maining motionless. The appearance of this one leaf 

 showed in an unequivocal manner that these minute 

 particles sufiiced to cause the tentacles to bend. Alto- 

 gether, ten such particles of hair were j)laced on ten 

 glands on several leaves, and seven of them caused 



