There are certain points of resemblance between communities of plants and those of human beings or animals; one of these is the competition for food which takes place between similar individuals and causes the weaker to be more or less suppressed. But far greater are the distinctions. The plant-community is the lowest form; it is merely a congregation of units, among which there is no co-operation for the common weal, but rather a ceaseless struggle of all against all. Only in a loose sense can we speak of certain individuals protecting others, as for example, when the outermost and most exposed individuals of scrub serve to shelter from the wind others, which consequently become taller and finer; for they do not afford protection from any special motive, such as is met with in some animal communities, nor are they in any way specially adapted to act as guardians against a common foe. In the plant-community egoism reigns supreme. The plant-community has no higher units or personages in the sense employed in connection with human communities, which have their own organizations and their members co-operating, as prescribed by law, for the common good. In plant-communities there is, it is true, often (or always) a certain natural dependence or reciprocal influence of many species upon one another; they give rise to definite organized units of a higher order; but there is no thorough or organized division of labor such as is met with in human and animal communities, where certain individuals or groups of individuals work as organs, in the wide sense of the term, for the benefit of the whole community. Woodhead has suggested the term _complementary association_ to denote a community of species that live together in harmony, because their rhizomes occupy different depths in the soil; for example, he described an "association" in which Holcus mollis is the "surface plant," Pteris aquilina has deeper-seated rhizomes, and Scilla festalis buries its bulbs at the greatest depth. The photophilous parts of these plants are "seasonably complementary." The opposite extreme is provided by _competitive associations_, composed of species that are battling with each other. 2. Ant Society[85] There is certainly a striking parallelism between the development of human and ant societies. Some anthropologists, like Topinard, distinguish in the development of human societies six different types or stages, designated as the hunting, pastoral, agricultural, commercial, industrial, and intellectual. The ants show stages corresponding to the first three of these, as Lubbock has remarked.