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Show 26 DROSERA ROTUNDIFOLIA. 0HAP. II. many of the other tentacles. yY' e here se~ clearly that such bodies as particles of cind r or httle balls of paper, after being carried by the tentacles to the central glands, act very differently from fragm nts of flies, in causing the movement of the surrounding tentacles. I made, without carefully recording the ti1nes of movement, many similar trials with oth r substances, such as splinters of white and blue glass, particles of cork, minute bits of gold-leaf, &c.; and the proportional number of cases varied much in 'vhich the tentacles reached the centre, or moved only slightly, or not at all. One evening, particles of glass and 1 cork, rather larger than those usually employed, were placed on about a dozen glands, and next morning, after 13 hrs., every single tentacle had carri d its little load to the centre; but the unusually large size of the particles will account for this result. · In another case f of the particles of cinder, glass, and thread, placed on separate glands, were carried towards, or actually to, the centre ; in another case *' in an ther 1 7 2 , and in the last case only -io- were thus carried inwards, the small proportion being here due, at least in part, to the leaves being rather old and inactive. Occasionally a gland, with its light load, could be seen through a strong lens to move an extremely short distanc and then stop; this was especially apt to occur when excessively minute particles, much less than those of which the measurements will be immediately given, were placed on glands; so that we here have nearly the limit of any action. I was so much surprised at the smallness of the particles .which caused the tentacl s to become great]y inflected that it seemed worth while carefully to ascertain how minute a particle would plainly act. CHAP. II. INFLECTION INDIRECTLY CAUSED. 27 Acco:·dingly measured lengths of a narrow strip of bl~tting paper, of nne cotton-thread, and of a woman's hau, we~·e carefully weighed for me by Mr. Trenham Reeks, In an excellent balance, in the laboratory in J e~myn Street. Short bits of the paper, thread," and hau were then cut off and measured by a micro t th t h . . me er, s~ a t eir weights could be easily calculated. The bits were placed on the viscid secretion surrounding th glands of the exterior tentacles, with the precaution: already stated, and I am · certain that the gland itself was never touched ; nor indeed would a single touch ha:e ~roduced any effect. A bit of the blotting-paper weighin g 4 t1J 5 of a grai·n , was p I aced so as to rest on' three g~ands together, and all three tentacles slowly cui:ved Inwards; each gland, therefore, supposing the we1ght to be distributed equally, could have been pressed on by only T-f95 of a grain, or ·0464 of a milligi~ amme. Five nearly equal bits of cotton-thread were tne.d, an~ all acted. The shortest of these was 5 1 0 of an Inch I~ leng_th, and weighed tin of a grain. The tentacle In this case was considerably inflected in 1 hr. 30m., 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 - 1 s f · h · 1 . . . 1 ot hoo o ha n Inc In ength, and weighing - ! __ of 35 ,1 ·1 ~grain, e ot er Tt%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_ t~e many other tentacles round the same leaf remaining. motionless. The appearance of this one leaf showed In an unequivocal manner that these minute particles sufficed to cause the tentacles to bend. Altogether, ten such particles of hair were placed on ten glands on several leaves, and seven of them caused |