As a rule, however, the number in a whorl is irregular.
When there is more than one row or whorl in a flower, those on the outside are sometimes longest, as in many Rosaceae; at other times those in the interior are longest, as in Luhea.
In the staminal whorl especially it is common to find additional rows.
B, C, D, E, enlarged.) branched rootstock from which spring slender aerial shoots which are green, ribbed, and bear at each node a whorl of leaves reduced to a toothed sheath.
The reduction of the tentacles in all these forms may be correlated with their mode of life, and especially with living in a constant current of water, which brings foodparticles always from one direction and renders a complete whorl or circle of tentacles unnecessary.
Xvii.), and in Clavatella each whorl consists regularly of eight (Allman, loc. cit.
Trophosome, polyps with a single whorl of capitate tentacles; gonosome, free medusae, with ten tacles branched, solid.
The trees have usually a straight trunk, and a tendency to a conical or pyramidal growth, throwing out each year a more or less regular whorl of branches from the foot of the leading shoot, while the buds of the lateral boughs extend horizontally.
31.-Shell of Crucibulum, seen coiled,but slightly in from below so as to show the inner whorl curved posteriorly; b, concealed by the cap-like outer whorl a.
Shell turriculated and siphonated, thick, each whorl with varices; foot broad and truncated anteriorly; pallial siphon well developed; proboscis present.
Shell thick, with short spire, last whorl large and canal short; aperture wide; operculum horny.
Terminating the short annual shoot which bears a whorl of four or more leaves below the flower; in this and in some species of the nearly allied genus Trillium (chiefly temperate North America) the flowers have a fetid smell, which together with the dark purple of the ovary and stigmas and frequently also of the stamens and petals, attracts carrion-loving flies, which alight on the stigma and then climb the anthers and become dusted with pollen; the pollen is then carried to the stigmas of another flower.
The members of the genus Larix are distinguished from the firs, with which they were formerly placed, by their deciduous leaves, scattered singly, as in Abies, on the young shoots of the season, but on all older branchlets growing in whorl-like tufts, each surrounding the extremity of a rudimentary or abortive branch; they differ from cedars (Cedrus), which also have the fascicles of leaves on arrested branchlets, not only in the deciduous leaves, but in the cones, the scales of which are thinner towards the apex, and are persistent, remaining attached long after the seeds are discharged.
An outer whorl of five opposite the petals alternates with an inner whorl of five opposite the sepals; at the base of each of the antisepalous stamens is a honey-gland.
In Erodium the members of the outer whorl are reduced to scale-like structures (staminodes), and in Pelargonium from two to seven only are fertile.
There is no satisfactory explanation of this break in the regular alternation of successive whorls; the outer whorl' of stamens arises in course of development before the inner, so that there is no question of subsequent displacement.
Pratense, each whorl of stamens ripens in turn, becoming erect and shedding their pollen; as the anthers wither the filaments bend outwards, and when all the anthers have diverged the stigmas become mature and ready for pollination.
The same occurs in the verticillate arrangement, the leaves of each whorl rarely being super- posed on those of the whorl next it, but usually alterna ting so that each leaf in a whorl occupies the space be tween two leaves of the whorl next to it.
Passing beneath rugged cliffs a recess in the hills is next reached, where stands Tubariya, the ancient Tiberias or Rakkath, containing 3000 inhabitants, more than half of whorl: are Jews.
In Coleochaetaceae the branches are often welded into nexion with each whorl there arise, singly or in pairs, branches which a plate, simulating a parenchyma.
Opposite to its lobes; this anomalous position is generally explained by assuming that an outer whorl of stamens opposite the sepals has disappeared, though sometimes represented by scales as in Samolus and Soldanella.
This structure was formerly regarded as pointing to the fusion of two organs, and the pale was considered by Robert Brown to represent two portions soldered together of a trimerous perianth - whorl, the third portion being the " lower pale."
The two bracts are, however, on different axes, one secondary to the other, and cannot therefore be parts of one whorl of organs.
They are generally considered to represent the inner whorl of the ordinary monocotyledonous b FIG.
The leaves are borne in whorls, those of each whorl cohering, except at their extreme tips, to form a sheath.
In some the sporangiophores stood midway between the sterile whorls, while in others they approached the whorl above or below.
At the base of the general umbel in umbelliferous plants a whorl of bracts often exists, called a general involucre, and at the base of the smaller umbels or umbellules there is a similar leafy whorl called an involucel or partial involucre.
The peduncle occasionally becomes abortive, and in place of bearing a flower, is transformed into a tendril; at other times it is hollowed at the apex, so as apparently to form the lower part of the outer whorl of floral leaves as in Eschscholtzia.
22, we recognize four distinct whorls of leaves: an outer whorl, the calyx of sepals; within it, another whorl, the parts alternating with those of the outer whorl, the corolla of petals; next a whorl of parts alternating with the parts of the corolla, the androecium of stamens; and in the centre the gynoecium of carpels.
The flower is supposed to be cut transversely, and the parts of each whorl are distinguished by a different symbol.
Thus, in the tulip, crocus, lily, speak of the parts of the perianth, in place of corolla, although in these plants there is an outer whorl (calyx), of three parts, and an inner (corolla), of a similar number, alternating with them.
Usually the successive whorls of the flower, disposed from below upwards or from without inwards upon the floral axis, are of the same number of parts, or are a multiple of the same number of parts, those of one whorl alternating with those of the whorls next it.
Normally, the parts of successive whorls alternate; but in some cases we find the parts of one whorl opposite or superposed to those of the next whorl.
In some cases, as in the vine-family Ampelidaceae, this seems to be the ordinary mode of development, but the superposition of the stamens on the sepals in many plants, as in the pink family, Caryophyllaceae, is due to the suppression or abortion of the whorl of petals, and this idea is borne out by the development, in some plants of the order, of the suppressed whorl.
23 is a diagram of a symmetrical flower, with five parts in each whorl, alternating with each other.
Here the number of parts in the staminal whorl is double that in the others, and in such a case the additional five parts form a second row alternating with the others.
36 there are three parts in each whorl; and in fig.
In Monocotyledons it is usual for the staminal whorl to be double, it rarely having more than two rows, whilst amongst dicotyledons there are often very numerous rows of stamens.
Flowers in which the number of parts in each whorl is the same, are isomerous (of equal number); when the number in some of the whorls is different, the flower is anisomerous (of unequal number).
The pistillate whorl is very liable to changes.
The dots represent a whorl of stamens which has disappeared.
When the different members of each whorl are like in size and shape, the flower is said to be regular; while differences in the size and shape of the parts of a whorl make the flower irregular, as in the papilionaceous flower, represented in fig.
When the parts of any whorl are not equal to or some multiple of the others, then the flower 15 asymmetrical.
Alteration in the symmetrical arrangement as well as in the completeness and regularity of flowers has been traced to suppression or the non-development of parts, degeneration or imperfect formation, cohesion or union of parts of the same whorl, adhesion or union of the parts of different whorls, multiplication of parts, and deduplication (sometimes called chorisis) or splitting of parts.
Cohesion, or the union of parts of the same whorl, and adhesion, or the growing together of parts of different whorls, are causes of change both as regards form and symmetry.
This takes place chiefly in the staminal whorl, but usually the additional parts produced form a symmetrical whorl with the others.
Thus in Cruciferous plants the staminal whorl consists of four long stamens and two short ones (tetradynamous).
33) would be represented by the formula S 5 P 5 St 5 + 5 C 5, where St5+5 indicates that the staminal whorl consists of two rows of five parts each.
Thus, to express the superposition of one whorl upon another, a line is drawn between them, e.g.
- Diagram to illustrate contorted or twisted aestivation, in which the parts of the whorl are overlapped by each other in turn, and are twisted on their axis.
S, the whorl of stamens inserted on the thalamus and surrounding the pistil.
Flowers become double by the multiplication of the parts of the corolline whorl; this arises in general from a metamorphosis of the stamens.
When flowers become double by cultivation, the stamens are converted into petals, as in the paeony, camellia, rose, &c. When there is only one whorl the stamens are usually equal in number to the sepals or petals, and are arranged opposite to the former, and alternate with the latter.
Changes are produced in the whorl of stamens by cohesion of the filaments to a greater or less extent, while the anthers remain free; thus, all the filaments of the androecium may unite, forming a tube round the pistil, or a central bundle when the pistil is abortive, the stamens becoming monadelphous, as occurs in plants of the Mallow tribe; or they may be arranged in two bundles, the stamens being diadelphous, as in Polygala, Fumaria and Pea; in this case the bundles may be equal or unequal.
It may consist of processes rising from the torus, alternating with the stamens, and thus representing an abortive whorl; or its parts may be opposite to the stamens.
The petaloid perianth consists of two series, each with three members, which are joined below into a longer or shorter tube, followed by one whorl of three stamens; the inferior ovary is three-celled and contains numerous ovules on an axile placenta; the style is branched and the branches are often petaloid.
The arrangement of the parts in the flower resembles that in the nearly allied order Amaryllidaceae (Narcissus, Snowdrop, &c.), but differs in the absence of the inner whorl of stamens.
As a rule, whenever we find the parts of one whorl superposed on those of another we may suspect some abnormality.
A flower is said to be symmetrical when each of its whorls consists of an equal number of parts, or when the parts of any one whorl are multiples of that preceding it.
- Diagram to illustrate reduplicative or reduplicate aestivation, in which the parts of the whorl are slightly turned outwards at the edges.
When there is more than one whorl of stamens, then the parts of each successive whorl alternate with those of the whorl preceding it.