Monographs Details:
Authority:
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Family:
Asteraceae
Asteraceae
Description:
Family Description - Individual fls epigynous, perfect or unisexual, sympetalous, regular or irregular, commonly 5- merous, without definite cal; stamens alternate with the cor-lobes, epipetalous, usually with elongate anthers united into a tube; ovary bicarpellate but unilocular, with a single erect ovule; style usually 2-cleft; fr an achene, unappendaged, or more commonly crowned with a pappus consisting of hairs or scales; fls sessile in a close head on a common receptacle, sometimes individually subtended by a small bract (chaff), and almost always collectively subtended by an invol of few to many bracts; our spp. annual to perennial herbs or rarely shrubs, the heads arranged in various sorts of basically determinate infls. (Compositae, nom. altern.) 1100/20,000. The invol bracts are usually herbaceous or subherbaceous in texture, varying to scarious, hyaline, coriaceous, or cartilaginous. They may be few and in a single row, or numerous and imbricate, or modified into spines, or even (as in Xanthium) concrescent into a bur. The receptacle may be chaffy, with a bract behind each fl (as in many Heliantheae), or may be covered with long, stout bristles (as in most Cynareae), or may be naked, without chaff or bristles. When naked it may sometimes be minutely pitted, with slender, chaffy partitions separating the pits, and is then said to be alveolate. It may even be softly hairy, as in some spp. of Artemisia. The fls are of several general types. In one type they are perfect (or functionally staminate) and the cor is tubular or trumpet-shaped or goblet-shaped, with typically 5 short lobes or teeth. This type of fl is called a disk-fl. A head composed wholly of disk-fls is said to be discoid. In another type the fl is pistillate or neutral (without a style), and the cor is tubular only at the very base, above which it is flat and usually bent backward so as to spread away from the center of the head. The flattened part of a cor of this type is called a ray or ligule, and the fl bearing it is called a ray-fl or ligulate fl. Often the ligules exhibit traces of 2 or 3 cor-lobes as small terminal teeth. Except for the pistillate heads of a few dioecious groups, the head is never composed wholly of fls of this type. Instead these pistillate or neutral ray-fls are found at the margin of the head, the center being occupied by the disk-fls. Such a head, with both ray-fls and disk-fls, is said to be radiate. In some spp. the ray or ligule of the marginal, pistillate fls does not develop, so that the cor is tubular. In addition to not bearing stamens, a cor of this type differs from the cor of an ordinary disk-fl in the absence of the regular terminal teeth, and often also in being more slender. A head in which the pistillate fls lack rays is said to be disciform, although the term discoid is sometimes loosely extended to cover this type. Another type of fl superficially resembles the ray-fl of a radiate head, but differs in being perfect and in usually having 5 terminal teeth on the ligule. The heads of the tribe Lactuceae consist wholly of fls of this type and are called ligulate heads. Ligulate perfect fls are rare in other tribes, and almost never make up the whole head. In some spp. of Centaurea the marginal fls are neutral and have an enlarged, irregular, ray-like cor. These fls are considered to be modified disk-fls. Members of the tribe Mutisieae (not represented in our region) usually have some fls with a bilabiate cor. The pollen-presentation mechanism is a characteristic feature of the family. The anthers are coherent by their lateral margins, or rarely merely connivent. The base of the anther varies from obtuse or subtruncate to broadly rounded, sagittate, or distinctly caudate (tailed). The anthers dehisce introrsely, and the pollen is pushed out through the anther-tube by growth of the style. The style-branches commonly diverge above the anther-tube, have various distinctive forms and texture, and tend to be stigmatic only on limited parts of their surface. The characteristic style- branches of the various tribes are to be sought only in the fertile disk-fls. The styles of ray-fls are mostly very similar in all groups, and those of sterile disk-fls are often reduced and undivided. The sterile disk-fls, when present, are said to be functionally staminate. Strictly staminate fls, with no pistillate parts, do not normally occur in the Asteraceae, because the style is necessary as a piston or plunger to eject the pollen.
Family Description - Individual fls epigynous, perfect or unisexual, sympetalous, regular or irregular, commonly 5- merous, without definite cal; stamens alternate with the cor-lobes, epipetalous, usually with elongate anthers united into a tube; ovary bicarpellate but unilocular, with a single erect ovule; style usually 2-cleft; fr an achene, unappendaged, or more commonly crowned with a pappus consisting of hairs or scales; fls sessile in a close head on a common receptacle, sometimes individually subtended by a small bract (chaff), and almost always collectively subtended by an invol of few to many bracts; our spp. annual to perennial herbs or rarely shrubs, the heads arranged in various sorts of basically determinate infls. (Compositae, nom. altern.) 1100/20,000. The invol bracts are usually herbaceous or subherbaceous in texture, varying to scarious, hyaline, coriaceous, or cartilaginous. They may be few and in a single row, or numerous and imbricate, or modified into spines, or even (as in Xanthium) concrescent into a bur. The receptacle may be chaffy, with a bract behind each fl (as in many Heliantheae), or may be covered with long, stout bristles (as in most Cynareae), or may be naked, without chaff or bristles. When naked it may sometimes be minutely pitted, with slender, chaffy partitions separating the pits, and is then said to be alveolate. It may even be softly hairy, as in some spp. of Artemisia. The fls are of several general types. In one type they are perfect (or functionally staminate) and the cor is tubular or trumpet-shaped or goblet-shaped, with typically 5 short lobes or teeth. This type of fl is called a disk-fl. A head composed wholly of disk-fls is said to be discoid. In another type the fl is pistillate or neutral (without a style), and the cor is tubular only at the very base, above which it is flat and usually bent backward so as to spread away from the center of the head. The flattened part of a cor of this type is called a ray or ligule, and the fl bearing it is called a ray-fl or ligulate fl. Often the ligules exhibit traces of 2 or 3 cor-lobes as small terminal teeth. Except for the pistillate heads of a few dioecious groups, the head is never composed wholly of fls of this type. Instead these pistillate or neutral ray-fls are found at the margin of the head, the center being occupied by the disk-fls. Such a head, with both ray-fls and disk-fls, is said to be radiate. In some spp. the ray or ligule of the marginal, pistillate fls does not develop, so that the cor is tubular. In addition to not bearing stamens, a cor of this type differs from the cor of an ordinary disk-fl in the absence of the regular terminal teeth, and often also in being more slender. A head in which the pistillate fls lack rays is said to be disciform, although the term discoid is sometimes loosely extended to cover this type. Another type of fl superficially resembles the ray-fl of a radiate head, but differs in being perfect and in usually having 5 terminal teeth on the ligule. The heads of the tribe Lactuceae consist wholly of fls of this type and are called ligulate heads. Ligulate perfect fls are rare in other tribes, and almost never make up the whole head. In some spp. of Centaurea the marginal fls are neutral and have an enlarged, irregular, ray-like cor. These fls are considered to be modified disk-fls. Members of the tribe Mutisieae (not represented in our region) usually have some fls with a bilabiate cor. The pollen-presentation mechanism is a characteristic feature of the family. The anthers are coherent by their lateral margins, or rarely merely connivent. The base of the anther varies from obtuse or subtruncate to broadly rounded, sagittate, or distinctly caudate (tailed). The anthers dehisce introrsely, and the pollen is pushed out through the anther-tube by growth of the style. The style-branches commonly diverge above the anther-tube, have various distinctive forms and texture, and tend to be stigmatic only on limited parts of their surface. The characteristic style- branches of the various tribes are to be sought only in the fertile disk-fls. The styles of ray-fls are mostly very similar in all groups, and those of sterile disk-fls are often reduced and undivided. The sterile disk-fls, when present, are said to be functionally staminate. Strictly staminate fls, with no pistillate parts, do not normally occur in the Asteraceae, because the style is necessary as a piston or plunger to eject the pollen.
Common Names:
The aster family
The aster family