Metamerism (biology)

Some schemes regard the concept of metamerism as one of the four principles of construction of the human body, common to many animals, along with general bilateral symmetry (or zygomorphism), pachymerism (or tubulation), and stratification.

As Asa Gray (1850) wrote:[6] The branch, or simple stem itself, is manifestly an assemblage of similar parts, placed one above another in a continuous series, developed one from another in successive generations.

I deem it essential to a correct philosophical understanding of the plant.Some plants, particularly grasses, demonstrate a rather clear metameric construction, but many others either lack discrete modules or their presence is more arguable.

[7] Eames (1961) concluded that "concepts of the shoot as consisting of a series of structural units have been obscured by the dominance of the stem- and leaf-theory.

[9] Metameric conceptions generally segment the vegetative axis into repeating units along its length, but constructs based on other divisions are possible.

[10] Vertical metamers are also suggested in some desert shrubs in which the stem is modified into isolated strips of xylem, each having continuity from root to shoot.