FLOWER, or BLossom, that part of a phanerogamous plant in which the organs of reproduction (stamens and pistils) are situated, and which consists essentially of a.Single group of these, generally surrounded by floral envelopes (the calyx and corolla). Both the organs of reproduction and the floral envelopes are metamorphosed leaves, and arise in successive whorls from a much shortened axis, called the thalamus (G•., a nuptial bed), or torus (Lat., a couch). Flowers are sometimes closely attached to the stem or branch from which they grow, and are then said to be sessile (Lat., sitting); but some times there intervenes a or peduncle, either simple or branched. The whole assemblage of flowers of a plant is called its inflorescence (q.v.), and the different kinds of inflorescence, or modes in which the flowers are produced and grouped, are often as characteristic as the diversities in the flowers themselves, although the latter are in gen eral more important with reference to botanical affinities.
In the very large natural order compositce, many small flowers are congregated on a com mon receptacle, and surrounded with bracts in the form of an involucre, as a single flower is surrounded by its calyx. The head of flowers is in this case popularly called a flower; and else individual flowers of which it is composed are by botanists styled florets. This term is also applied to the individual flowers in the spikelets of the grasses (q.v.), of which the glumes are a common involuere.
The order of the whorls in flowers is invariable: the calyx (q.vi) is always exterior to the corolla in within the corolla are the stamens (q.v.), or male organs of repro duction; and n the center of all is the pistil (q.v.), the female organ of reproduction. An outer calyx, or whorl of metamorphosed leaves, exterior to the calyx, and usually smaller, is found in some flowers, as mallows, and is called, the epicaly.c. Within the corolla, there is sometimes an additional or supplementary corolla, called the corona (q.v.), coronet, or crown. When the calyx and corolla are not easily distinguishable, the term perianth (q.v.), or perigone, is employed, as in the lily, crocus, iris, and the greater
number of endogenous plants, although even in these there are really two whorls closely united. In some flowers, there arc several whorls of leaves forming one or each of the floral envelopes; and in like manner, some have several whorls of stamens, and some times there are several whorls of the carpels which form the pistil. In seine flowers, certain whorls are entirely wanting; and thus not a few exogenous plants are destitute of the corolla, which is sometimes the case with plants—exceptional apetalous species— very nearly allied to others that have it. It is by a similar abortion of a whorl that flowers become unisexual. • Both stamens and pistils are rrenerally present in the same flower, which is called a hermaphrodite or perfect flower; but many flowers contain only the male organs of reproduction, and many contain only the female organs. and such flowers are described as unisexual, diclinous (q.v.), or imperfect; and respectively as male or staminiferous, and female or pistilliferous flowers. Male flowers are also called barren or sterile, and female flowers fertile, although their fertility depends on the communica tion of pollen from the staminiferous flowers.. When both male and female flowers are produced on one plant, the species is said to be moncecious (Gr., having one house); hut when they are on separate plants, it is diacious (Gr., having twe houses); those which produce male, female, and hermaphrodite flowers are called polygamous. Sometimes both stamens and pistils are wanting, and the flower is then said to be neuter or empty, as. in the case of the florets of the ray in many composite flowers. Sometimes, on the contrary, both calyx and corolla are wanting. and then the flower is said to be naked or acklamydeous (Gr., without covering), as flowers having on:v one floral envelope are called monochlamydeous, and flowers having both calyx and corolla are called dichla mydeous. Achlamydeous flowers are often grouped in some peculiar manner, and pi•o tected by bracts or by a spathe.