. Popular science monthly. en from an excellentphotograph made for me by , of Bromley. The plantson the right are true stinging-nettles ; those on the left are thewhite dead-nettle, one of whichis in flower. So close was the re-semblance that, after getting thephotograph, I went back to thespot on which they were growingto assure myself that there was nomistake. It can not be doubtedFig. 21. that the true nettle is protected by its power of stinging ; and, thatbeing so, it is scarcely less clear that the dead-nettle must be protectedby its likeness to the other. Moreover, though I was
. Popular science monthly. en from an excellentphotograph made for me by , of Bromley. The plantson the right are true stinging-nettles ; those on the left are thewhite dead-nettle, one of whichis in flower. So close was the re-semblance that, after getting thephotograph, I went back to thespot on which they were growingto assure myself that there was nomistake. It can not be doubtedFig. 21. that the true nettle is protected by its power of stinging ; and, thatbeing so, it is scarcely less clear that the dead-nettle must be protectedby its likeness to the other. Moreover, though I was fortunate in light-ing on so good an illustration as that shown in the figure just when Ihad the opportunity of photographing it, still every one must have ob-served that the two species are very commonly found growing to-gether. Assuming that the ancestor of the dead-nettle had leavespossessing a faint resemblance to those of the true nettle, those inwhich the likeness was greatest would have the best chance of survival,. ON LEAVES. 483 and consequently of ripening seeds. There would be a tendency,therefore, according to the well-known principles of Mr. Darwin, to acloser and closer resemblance. I am disposed to suggest whetherthese resemblances may not serve as a protection, not only frombrowsing quadrupeds, but also from leaf-eating insects. On this partof the subject we have as yet, however, I think, no sufficient observa-tions on record. Ajuga chamcepitys, the yellow bugle, has leaves crowded anddivided into three linear lobes, the lateral ones sometimes againdivided. They differ, therefore, greatly from those of its allies, andthis puzzled me much until one day I found it growing abundantlyon the Riviera among Euphorbia cyparissias, and I was much struckby the curious likeness. The Euphorbia has the usual acrid juiceof the genus, and it struck me that the yellow ajuga was perhapsprotected by its resemblance. Leaves which float on the surface of still water tend to be orb
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
