Besides the family likeness and similarity of structure characteristic of closely allied organisms, other resemblances included under the terms Mimicry and Homomorphism, are observed among living things which can not be referred to a common ancestry since they are presented by plants and animals whose affinities are more or less remote. If the resemblance confers any benefit on either species it is spoken of as a case of mimicry, but if it results from the operation of general laws and is not directly advantageous, the likeness is described as homomorphic. It is not always possible to draw a sharp line between the two, and homomorphism not improbably represents one stage in the development of mimetic species. The vital phenomena of plants and animals are so near akin that it would be strange if we did not meet with corresponding facts in the vegetable kingdom. Mimicry is perhaps more frequent in the seed than in any other part of vegetable organism; it occurs, however, in other organs, and even the entire plant body may assume a deceptive appearance. A well-known example is the white dead-nettle, which so closely resembles the stinging nettle in size and in the shape and arrangement of its leaves. In systematic position the two plants are widely removed from each other, but they grow in similar situations and are easily mistaken; any one who has occasion to collect any quantities of Lamium is almost sure to get his hands stung by Urtica, an experience calculated to convince one of the efficacy of protective resemblance. Among animals it is species provided with formidable weapons of defence that are most frequently mimicked by weak defenceless creatures. The stinging nettle is therefore a very likely model for unprotected plants to copy. A somewhat analogous case is the yellow bugle of the Riviera, which has its leaves crowded and divided into three linear lobes, some of which are again divided. In this the plant differs very greatly from its allies; it has, however, acquired a very striking resemblance to a species of Euphorbia, abundant on the Riviera. The acrid juice of the Euphorbias secures them immunity against a host of enemies. As the two plants grow together there is little room to doubt that, like the dead-nettle, the bugle profits by its likeness to its well protected neighbor. The rare heath Menziesia cærulia, thought to be protected by its marked resemblance to the crowberry (Empetrum nigrum), has also been adduced as a probable case of mimicry. Mr. A. R. Wallace in _Tropical Nature_ refers to the stone mesembryanthemum at the Cape described by Dr. Burchell, which closely resembles in form and color the stones among which it grows; on this account the discoverer believes this juicy little plant generally escapes the notice of cattle and wild herbivorous animals.