VI 
COLOURS OF PLANTS 
397 
of cattle and wild herbivorous animals. Mr. J. P. Mansel 
Weale also noticed that many plants growing in the stony 
Karoo have their tuberous roots above the soil, and these so 
perfectly 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 be 
protective mimicry have^lso been noted, the most curious 
being that of three very rare British fungi, found by Mr. 
Worthington Smith, each in company with common species 
which they so closely resembled that only a minute examina- 
tion could detect the difference. One of the common species 
is stated in botanical works to be “ bitter and nauseous,” so 
that it is not improbable that the rare kind may escape being 
eaten by being mistaken for an uneatable species, though 
itself palatable. Mr. Mansel Weale also mentions a labiate 
plant, the Ajuga ophrydis, of South Africa, as strikingly 
resembling an orchid. This may be a means of attracting 
insects to fertilise the flower in the absence of sufficient nectar 
or other attraction in the flower itself ; and the supposition is 
rendered more probable by this being the only species of the 
genus Ajuga in South Africa. Many other cases of resem- 
blances between very distinct plants have been noticed — as that 
of some Euphorbias to Cacti; but these very rarely inhabit the 
same country or locality, and it has not been proved that there 
is in any of these cases the amount of inter-relation between 
the species which is the essential feature of the protective 
“ mimicry ” that occurs in the animal world. 
The different colours exhibited by the foliage of plants 
and the changes it undergoes during growth and decay, 
appear to be due to the general laws already sketched out, 
and to have little if any relation to the special requirements 
of each species. But flowers and fruits exhibit definite and 
well-pronounced tints, often varying from species to species, 
and more or less clearly related to the habits and functions of 
the plant. With the few exceptions already pointed out, 
these may be generally classed as attractive colours. 
Attractive Colours of Fruits 
The seeds of plants require to be dispersed so as to reach 
places favourable for germination and growth. Some are 
