On this theory colour is regarded as due to the presence of a " chromophore," and dyeing power to an " auxochrome "; the latter by itself cannot produce colour or dyeing power, but it is only active in the presence of a chromophore, when it intensifies the colour and confers the property of dyeing.
He points to the fact that the imminence of death often intensifies instead of diminishing a man's desire for the welfare of those he loves, as a crucial experiment proving the disinterestedness of love; adding, as confirmatory evidence, that the sympathy and admiration commonly felt for self-sacrifice depends on the belief that it is something different from refined self-seeking.
The greatest difference of opinion exists among botanists as to their number and the bounds to be assigned to each; and the cross-fertilization that takes place between the species intensifies the difficulty.
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