208 



NATURE 



\_7uly 12, 1877 



hesitation, stale that in the whole flock, old and young, I could 

 not find a single living insect, or the germ of one." 



In the month of March last, agreeably to my promipe, I issued 

 a faithful report of the results of this system of stamping out 

 insect life. The sheep cleansed on this principle were absolutely 

 clear of insect pests, whilst others not so treated were never free. 

 I shall send with pleasure this report to any of your readers who 

 may desire to have it. 



I believe I may say there is exact analogy between this system 

 for extennin.iling insect life in animals and that adopted by Dr. 

 Tyndall to show that the eailiest eggs or gtrms of bacteria are 

 extremely obstinate to kill, whilst the more fully developed are 

 destroyed without difficulty, clearly showing that more than one 

 treatment is necessary for the complete destruction of germ life 

 as well as for a higher form of insect life, and that the same law 

 applies to both alike. 



I am fully convinced of the possibility of stamping out noxious 

 insects that affect .sheep and other animals, and sincerely hope 

 Mr. Murray's suggestion at the Society of Arts of united action 

 to effect thispurposeunder the direction of science and experience 

 may be acted upon with little delay. W. Little 



The Hall, Heckington, Lincolnshire 



Complementary Colours 



In Nature (vol. xvi. p. 150) you give a most interesting, 

 though very brief, account of Prof. Rood's researches on colour, 

 the result of which you sum up in these words : — • 



"The mixture with white is the same as if the colours were 

 moved towards the violet end of the spectrum." 



I know of Prof. Rood's results only from your abstract, but 

 your summary is not a perfectly accurate account of the facts 

 which you state immediately before, unless the expression 

 "violet end" is to be used in a new sense, or, v,^hat would be 

 better, replaced by the expression, "violet ;^('/i>." 



The following will be found a correct summary of Prof. 

 Rood's results : — 



Let the colours of the spectrum be arranged, not in a line but 

 in a circle, and the gap between red and violet be filled up with 

 purple. Each colour will then be opposite to its complementary 

 colour. Greenish yellow and violet, which are mutually com- 

 plementary, are the opposite pole.s, and the succession will be 

 as follows : — 



Greenish yellow. 

 Yellow. Yellowish green. 



Orange. Green. 



Vermilion. Cyanogen blue. 



Purple. Cobalt blue. 



Ultramarine. 

 Violet. 



The addition of violet to any one of the colours except those at 

 the two poles will bring that colour nearer to the violet pole ; 

 the same addition to either of the polar colours will leave them 

 unchanged as to their position in the circle. The addition of 

 white will have the same effect. 



As regards the effect ot the addition of violet, this is what we 

 might expect. Violet added to violet will only make violet. 

 Vii)let added in small quantities to greenish yellow, which is its 

 complementary, will only make it whiter without changing the 

 colour. Violet added to any other colour will bring it nearer to 

 violet. Vile might select any pair of complementaries as poles, 

 and obtain a parallel result. But what is new, and if confirmed, 

 most important, is that white has the same effect as violet. I 

 can sugiJest no explanation of this. 



For the fact tliat every colour in the spectrum has its comple- 

 mentary, see Prof. Grassmann in the Philosophical Ma_^azhie of 

 April, 1854. Hispaper appears to be less known than it deserves. 

 The pairs of complementaiies according to him are as follows ; — 



Red. 

 Orange. 

 Yellow. 



Yellowish green. 

 Green. 



Bluish green. 



Azure. 

 Indigo. 

 V'iolet. 

 Purple. ' 



Most authorities say that purple is not to be found in the spec- 

 trum, but Grassman says that under favourable conditions of 

 light it may be. I think that in any observations on the subject 

 where great accuracy is desired, the use of sunlight is to some 



extent mi'sleading, and that the true white is that of an incan- 

 descent solid or liquid at a very high temperature — that is to say 

 the electric light. The sun's light is such a light where it leaves 

 the body of the sun, but part of its rays are absorbed in the sun's 

 atmosphere, and the blue in greater proportion than the red and 

 yellow ; and a further loss of blue rays takes place in the earth's 

 atmosphere by scattering, forming the blue of the sky. The blue 

 light of the sky is taken out of the white light of the sun. For 

 these two reasons the sun's light at the surface of the earth is not 

 truly white but yellowish. 



I can scarcely doubt that when the spectrum of the electric light 

 is carefully examined, it will be found to contain purple ; and 

 also that some simple mathematical relation will be discovered 

 between the wave-lengths of every colour and its comple- 

 mentary. JosEi'n John Murphy 



Old Forge, Dunmurry, co. .\ntrim, Jane 24 



Phyllotaxis 



The theory which regards the alternate arrangement of leaves 

 as the normal mode receives some support from the arrangement 

 of the inflorescence of opposite leaved plants. In Lysimachia 

 nemorum the leaves are opposite, inflorescence indefinite, 

 solitary, and axillary, but it will be observed that the flowers 

 springing Irom the axils of opposite leaves are never both equally 

 developed at the same time, one will be fully expanded while the 

 other is yet in bud, or one will be found in seed and the other in 

 flower ; it will be further observed that the oldest or most fully 

 developed flower appears alternately on opposite sides of the 

 stem ; if all the leaves on this plant were separated by internodes, 

 the arrangement would be tetrastichous, but owing to the sup- 

 pression of the internodes between the first and second and the 

 third and fourth leaves, the arrangement becomes opposite. The 

 oldest of the two opposite flowers of each pair of leaves will be 

 found to spring from the axil of the first, third, and fifth leaf, and 

 plants with this alternate di-posilion of flowers may sometimes be 

 met with ; but usually a flower originates in the axil of each leaf, 

 and then the youngest or late-t flowers spring from the second 

 and fourth leaves of the verticil ; these latter may be looked upon 

 as originating from arrested branches. This view is supported by 

 the fact that plants may be sometimes found which, in place of 

 producing the late flowers in the axils of the third and fourth 

 leaves, produce branches from these points instead. In Cayyo- 

 phyllaccr the opposite sides of the cymose inflorescence never 

 exhibit an equal amount of development at the same time, 

 proving that one of the sides is older than the other, although, 

 owing to non-development of an intemode, it is at the same level. 

 A similar arrangement occurs in Labiate plants, but owing to 

 the crowded inflorescence, it is not so evident, but it is very 

 marked where branches spring from opposite leaves ; one is 

 generally two or three times as long as the other, and by tracing 

 the arrangement of these long branches along the stem, the 

 normal alternate arrangement may be determined. In Scrophit- 

 lariaetii^ where both opposite and alternate leaves are met with, 

 all the above-mentioned modifications may be seen. Veronica 

 ckama'dyys has opposite leaves, and when the axillary racemes 

 are opposite, one is invariably more developed than the other ; 

 this can be best seen by examining the inflorescence in the young 

 state, as the dissimilarity in size disappears in the pairs of old 

 racemes owing to the younger of the two continuing to grow 

 until it has acquired the size of the other ; sometimes this plant 

 may be met with bearing in the axil of one of its opposite leaves 

 a branch, and a raceme of flowers in the other, and in such 

 instances the branches and flowers are produced on alternate 

 sides ; in /'. officinalis this is the usual arrangement. The 

 suppression of the alternate nodes of an alternate-leaved plant 

 with axillary inflorescence would produce the arrangement seen 

 in Lysimachia, inasmuch as it would bring ^together flowers ot 

 different ages and in different stages of expansion ; but in this 

 instance all the flowers would belong to the same generation or 

 be the product of the same stem, wlrereas in Lysimachia the 

 earliest developed of each pair of opposite flowers alone belong 

 to the stem, while the later flower of each pair belong to another 

 generation, and spring from a branch originating in the axil of 

 the leaf opposite (owing to non-development of an internode) to 

 the early flower ; the branch, however, is generally arrested, and 

 the flower alone appears, although sometimes the branch is more 

 or less developed. 



G. E. Massee 



