COLOURS OF PLANTS. 



223 



specialised in the several genera and species of tlie 

 vegetable kingdom. 



Protective Coloration and Mimicry in Plants. — In 

 animals, as we have seen, colour is greatly influenced by 

 the need of protection from, or of warning to, their 

 numerous enemies, and by the necessity for identification 

 and easy recognition. Plants rarely need to be concealed, 

 and obtain protection either by their spines, their hard- 

 ness, their hairy covering, or their poisonous secretions. 

 A very few cases of what seem to be true protective 

 colouring do, however, exist ; the most remarkable being 

 that of the ' ' stone mesembryanthemum,'' of the Cape of 

 Good Hope, which, in form and colour closely resembles 

 the stones among which it grows ; and Dr. Burchell, who 

 first discovered it, believes that the juicy little plant thus 

 generally escapes the notice 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 also 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 examination could detect the difierence. 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 lal^iate plant, the Ajuga- 



