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vi COLOURS OF PLANTS 897of cattle and wild herbivorous animals. Mr. J. P. ManselWeale also noticed that many plants growing in the stonyKaroo have their tuberous roots above the soil, and these soperfectly resemble the stones among which they grow that,when not in leaf, it is almost impossible to distinguish them(Nature, vol. iii. p. 507). A few cases of what seems to beprotective mimicry have also been noted, the most curiousbeing that of three very rare British fungi, found by Mr.Worthington Smith, each in company with common specieswhich they so closely resembled that only a minute examinationcould detect the difference. One of the common speciesis stated in botanical works to be " bitter and nauseous," sothat it is not improbable that the rare kind may escape beingeaten by being mistaken for an uneatable species, thoughitself palatable. Mr. Mansel Weale also mentions a labiateplant, the Ajuga ophrydis, of South Africa, as strikinglyresembling an orchid. This may be a means of attractinginsects to fertilise the flower in the absence of sufficient nectaror other attraction in the flower itself ;and the supposition isrendered more probable by this being the only species of thegenus Ajuga in South Africa. Many other cases of resemblancesbetween very distinct plants have been noticed as thatof some Euphorbias to Cacti; but these very rarely inhabit thesame country or locality, and it has not been proved that thereis in any of these cases the amount of inter-relation betweenthe species which is the essential feature of the protective" "mimicry that occurs in the animal world.The different colours exhibited by the foliage of plantsand the changes it undergoes during growth and decay,appear to be due to the general laws already sketched out,and to have little ifany relation to the special requirementsof each species. But flowers and fruits exhibit definite andwell-pronounced tints, often varying from species to species,and more or less clearly related to the habits and functions ofthe plant. With the few exceptions already pointed out,these may be generallyclassed as attractive colours.Attractive Colours of FruitsThe seeds of plants require to be dispersed so as to reachplaces favourable for germination and growth. Some are