ELECTRICITY. 



obtained was greenish and of peculiar aspect, 



in which tlio spectroscope showed neither the 

 rays of bromine nor those of tin perdilori<le, 

 but only the three well-known bands usually 

 attributed to the spectrum of carbon. These 

 bands are the same which Yogel and other 

 observers have designated as forming 'the 

 spectrum of comets. Besides, the luminous 

 column thus produced gave rise, not to a 

 plu-nomenon of attraction, but to a very well- 

 detiuetl repulsion. The authors, after re- 

 peated experiments, are firmly convinced that 

 these curious phenomena are due to the ex- 

 treme rarefaction of the gases employed ; and, 

 since the gus forming the tails of comets is 

 undoubtedly in a state of high rarefaction, 

 they conclude that this is the cause of the 

 repulsion of the sun on the comet's tail, the 

 sun being then considered simply as a good 

 conductor. 



Electrical Phenomena in Plants. The leaf 

 of the plant Dioncea muscipula, one of the 

 carnivorous plants, has been found by Dr. 

 Burdon-Sundersou to possess an electro-mo- 

 tive action. The same author has shown that 

 when contraction takes place in the , leaf there 

 is a negative variation of the current ; he has 

 also observed in the leaf something corre- 

 sponding to the latent stimulation of muscles 

 and the electrotonus of nerves. This subject 

 has lately been investigated by Hermann Munk, 

 whose results have been published in Der Na- 

 turforscher. Briefly they may be stated as 

 follows: 



Applying the unpolarizable electrodes to the under 

 surface of a leaf, a current appears in (say) an up- 

 ward direction, i. e., flowing in the leaf from tlie end 

 of the petiole or leaf-staik (call it the fore-end of the 

 loaf) to the free end or point of the leaf (which 

 may be called the hituler end). Points situated sim- 

 ilarly on the two halves of the leaf are homogeneous, 

 hence on the two sides of the midrib all is symmet- 

 rical. Conceive the midrib divided into two un- 

 equal parts t a shorter hinder part and a longer fore 

 part ; then in each of these parts every point nearer 

 the inner end is positive to every more distant point. 

 Tlic most positive point of the midrib lies about the 

 fore-end of its hindermost third, and with increas- 

 ing distance from this point the positively decreases 

 toward botb ends. 



Suppose lines drawn on the surface of a half-leaf 

 at right angles to the midrib ; and call these cross- 

 lines of the leaf. Every point of such a cross-line 

 proves negative to the corresponding point of the 

 midrib ; and regularly the negativity of these points 

 increases first to a maximum, and then, on to the 

 outer leaf-border, decreases. The most negative 

 point of the cross-line never coincides with the mid- 

 ale of the line, but is always nearer the leaf-border 

 than the midrib. 



By connecting the most negative points of all the 

 sections, we have a principal line of length nearly 

 parallel to that of the midrib. All points in this 

 lino are homogeneous. So also are related points 

 of other lines of length running parallel to the mid- 

 rib, and lying inward from tne principal length- 

 line. Of the middle parts of two cross-lines, which 

 are l>oth in the fore or both in the hinder halves of 

 the leaf-halves, the middle nearer to the fore or to 

 the hinder leaf-border respectively is always posi- 

 tive to the more distant middle, and the force, down- 

 ward in the former case, upward in the latter, in- 



creases with the width of span of the arch. The 



principal length-line, then, in the sum <>\ the moi-i 

 ncgutive points of each leaf-half, while in opposi- 

 tion is the most positive point of the leaf at the 

 tun -<iid of the hinderniost third of the midrib. 

 An. I, us in the whole leaf all in symmetrical on 

 tin' two sides of the midrib, BO in each leaf-half all 

 is symmetrical on the two side* of the middle cross- 

 line. The complete symmetry of the leaf seems to 

 bo disturbed only in that the most pobitive point in 

 the midrib is displaced back from the middle. 



The examination of the upper surface of the leaf 

 offers great difficulties, owing to its sensitiveness. 

 These naving been overcome, it is found that the 

 same .distribution of tensions prevails as on the 

 under surface. 



The source of the electro-motive action he 

 supposes to reside in the interior of the leaf, 

 nor can it, according to him, arise from hetero- 

 geneity of surface. The primary organs of the 

 electric forces are neither the disk-glands, the 

 hairs, the fibro-vascular cords, nor the epider- 

 mis, but the cylindrical cells of the parenchyma 

 in the halves of the leaf and in the midrib. 

 These cells are endowed with forces of such a 

 kind that the positive electricity is driven from 

 the middle of the cell to each of the two poles, 

 which are positive poles to the middle. 



The mechanical movements of the plant are of 

 two kinds : stimulation movements, and reeorption 

 movements. In the former, the leaf closes very 

 quickly after stimulation, within a minute or so, all 

 parts moving simultaneously. In a few hours it 

 begins to open again, and is quite open after twenty- 

 four to thirty-six hours. It is then susceptible of 

 further stimuliition. The resorption movement, on 

 the other hand, is more rare, and occurs when a 

 small piece of flesh, albumen, or the like, is care- 

 fully laid on the leal-surface, avoiding the sensitive 

 hairs. The closure which follows is very slow, not 

 beginning for some hours, and being completed only 

 in one to two days. The movements of the two 

 halves are irregular and unsimultaneous, and depend 

 on the place of contact, from which they spread 

 outward. The reopening begins after several days, 

 and takes several days to be completed ; and during 

 this time the leaf is not, or is very little, susceptible 

 of either stimulation or resorption movements. The 

 leaf may die after one such resorption movement, 

 and two or three always prove fatal to it ; it opens 

 no more. 



We now come to the electrical phenomena in stim- 

 ulation, of which Dr. Sanderson said that they 

 presented a negative variation similar to that of the 

 muscle-current. The electrodes were placed on the 

 under surface of the midrib, as being the onlv part 

 of the leaf which, during movement of the latter, 

 docs not alter in position. On stimulation through 

 movement of the sensitive hair, there occurs, not * 

 simple negative variation, but, as the author ex- 

 presses it, a positive variation with negative primary 

 impulse, which he calls double variation. This 

 electrical phenomenon occurs even when, notwith- 

 standing stimulation, there is no movement of the 

 . leaf. The latter circumstance renders possible an 

 examination also of the leaf parenchyma; and the 

 same double variation is here observed. 



As to the explanation of this double variation, the 

 supposition that all the cells pass first through a 

 negative, then through a positive variation, is to be 

 n j.cted; the process is rather (the author thinks) 

 that through stimulation the cells of the upper 

 halves of the half-leaf parenchyma and of the upper 

 midrib parenchyma experience a negative variation, 

 those or the under halves of the half-leaf parenchy- 

 ma and of the under midrib parenchyma a positive ; 

 that is, the negativity of the middle of the cells U 



