Distribution by seed appears to satisfy so well the requirements of Angiosperms that distribution by vegetative buds is only an occasional process.  At the same time every bud on a shoot has the capacity to form a new plant if placed in suitable conditions, as the horticultural practice of propagation by cuttings shows; in nature we see plants spreading by the rooting of their shoots, and buds we know may be freely formed not only on stems but on leaves and on roots.  Where detachable buds are produced, which can be transported through the air to a distance, each of them is an incipient shoot which may have a root, and there is always reserve-food stored in some part of it.  In essentials such a bud resembles a seed.  A relation between such vegetative distribution buds and production of flower is usually marked.  Where there is free formation of buds there is little flower and commonly no seed, and the converse is also the case.  Viviparous plants are an illustration of substitution of vegetative buds for flower.

Phylogeny and taxonomy.

The position of Angiosperms as the highest plant-group is unassailable, but of the point or points of their origin from the general stem of the plant kingdom, and of the path or paths of their evolution, we can as yet say little.

Until well on in the Mesozoic period geological history tells us nothing about Angiosperms, and then only by their vegetative organs.  We readily recognize in them now-a-days the natural classes of Dicotyledons and Monocotyledons distinguished alike in vegetative and in reproductive construction, yet showing remarkable parallel sequences in development; and we see that the Dicotyledons are the more advanced and show the greater capacity for further progressive evolution.  But there is no sound basis for the assumption that the Dicotyledons are derived from Monocotyledons; indeed, the palaeontological evidence seems to point to the Dicotyledons being the older.  This, however, does not entitle us to assume the origin of Monocotyledons from Dicotyledons, although there is manifestly a temptation to connect helobic forms of the former with ranal ones of the latter.  There is no doubt that the phylum of Angiosperms has not sprung from that of Gymnosperms.

Within each class the flower-characters as the essential feature of Angiosperms supply the clue to phylogeny, but the uncertainty regarding the construction of the primitive angiospermous flower gives a fundamental point of divergence in attempts to construct progressive sequences of the families.  Simplicity of flower-structure has appeared to some to be always primitive, whilst by others it has been taken to be always derived.  There is, however, abundant evidence that it may have the one or the other character in different cases.  Apart from this, botanists are generally agreed that the concrescence of parts of the flower-whorls—­in the gynaeceum as the seed-covering, and in the corolla