130 BOTANY [REPRODUCTIVE ORGANS. pentamerous symmetry, the whorls being Uomerous. Such a flower as that of Sedum (fig. 180) would be represented by the formula S 5 P 5 St 6+s C s , where St 5+5 indicates that the staminal whorl consists of two rows of five parts each. A flower such as the male flower of the Nettle (fig. 188) would be expressed S 4 P St 4 C . It is also possible to indi cate, in cases where members of a whorl are absent, which of them are wanting ; thus, in the flower of an Orchis we have S. i P. j St 1+0 C. i . Here Sti +0 indicates that the anterior stamen of the outer row is present, the other two stamens of the row, marked as dots, are wanting, as also all the stamens of the inner row. In Cypripedium, on the other hand, the formula is S ;! P 3 St 0+2 C 3 , for here all the stamens of the outer row and the anterior one of the inner row are absent. When no other mark is appended the whorls are supposed to be alternate ; but if it is desired to mark the position of the whorls special symbols are employed. Thus, to express the superposition of one whorl upon another, a line is drawn between them, e.g., the symbol S P 3 | St 5 C s is the formula of the flower of Primulacea?. To indicate the interposition of a row of parts in a whorl a dot is placed between the coefficients, thus S 5 P 5 St 5 . 5 C 5 indicates that an extra row of five stamens has been interposed between those already in existence. To represent adhesions and cohesions leads to complicated formulae, but in many cases cohesion A A A can be easily indicated. Thus in the formula S. 1 P 4 St.,C 2 , we have the arrangement of the parts of the flower in Veronica indicated, the sepals and the petals being united and the two carpels also being united into one pistil. The papilionaceoui flower, of which fig. 18G is a diagram, may be formulated We thus learn that there are five sepals united, five free petals, ten stamens in two rows, of which are united and one is free, and there is one carpel. nn When the parts of the flower are arranged spirally on the floral axis, as in Magnoliacese and other flowers, the formula is prefixed by a curved line thus C ->, and then the angle of divergence of the members may be marked in addition to their number. Many other points in the arrangement of the flower may be attached to the formula by different symbols, according to the object which one has in view. Fig. 188. Fig. 189. Fig. 190. FIG. 188. Tetramerous male (unisexual) flower of the Nettle (Urticti) It is in- W P PTI u^ T ^ S pCt lls and P istil ; a nd it is said to be monochlamydeotis. ho P t JTf h . 6 axlS Md is callcd P ost e"or or superior, another is next and left ToVtheax is nferior . and two are lateral, that is, to the right 1 aiV^aTp^ff?? "? "JSS"* 6 * 7 " 17 ^?! valyate activation, in which theparts aie i placed m a circle, without overlapping or folding. the T mrts : of a ?iu. n J-MMMl lS , trat v il J^ p l icath , e or indu Pcate aestivation, in which he verticil are slightly turned inwards at the edges. _ To the flower-bud the name alabastrus is sometimes given and its period of opening has been called anthesis, the manner in which the parts are arranged with respect to each other before opening is the estivation or Defloration, The latter terms are applied to the flower- ad in the same way as vernation is to the leaf-bud, and stinctive names have been given to the different arrange ments exhibited, both by the leaves individually and in their relations to each other. As regards each leaf of the lower, it is either spread out, as the sepals in the bud of
- Lime-tree or folded upon itself (conduplicate), as in
the petals of some species of Lysimachia, or Sightly d inwards or outwards at the edges, as in the calyx of some species of Clematis, -and of some herbaceous plants, or rolled up at the edges (involute or revolute), or folded transversely, becoming crumpled or corrw/ati d, as in the Poppy. When the parts of a whorl are placed Plate I. in an exact circle, and are applied to each other by their edges only, without overlapping or being folded, thus re sembling the valves of a seed-vessel, the aestivation is valvate, as in the calyx of Guazuma ulmifolia (fig. 189). The edges of each of the parts may be turned either inwards or outwards ; in the former case, the aestivation is induplicate, as in the corolla of Guazuma ulmifolia (fig. 190), in the latter case, reduplicate, as in the calyx of Althaea rosea (fig. 191). When the parts of a single whorl are placed in a circle, each of them exhibiting a torsion of its axis, so that by one of its sides it overlaps its neighbour, whilst its side is overlapped in like manner by that standing next to it, the aestivation is twisted or contortive, as in the corolla of Althaea rosea (fig. 192). This arrangement is characteristic of the flower-buds of ? 191- Fig. 192. Fig. 193. FIG. 101. -Diagram to illustrate reduplicative or reduplicate aestivation, in which the parts of the whorl are slightly turned outwards at the edges. .Diagram to illustrate contortive or twisted aestivation, in which the parts of the whorl are overlapped by each other in turn, and are twisted on their axis. FIG. ] 93. Diagram to illustrate the quincnncial aestivation, in which the parts ! the flower are arranged in a spiral cycle, so that 1 and 2 are wholly ex ternal, 4 and 5 are internal, and 3 is partly external and partly overlapped Malvaceae and Apocynaceae, and it is also seen in Con- volvulaceae and Caryophyllaceco. When the flower expands, the traces of twisting often disappear, but sometimes, as in Apocynacese, they remain. Those forms of aestivation are such as occur in cyclic flowers, and they are included under circular aestivation. But in spiral flowers we have a different arrangement, the leaves of the calyx of Camellia japonica cover each other partially like tiles on a house. This aestivation is imbricate. At other times, as in the petals of Camellia, the parts envelope each other completely, so as to become convolute. This is also seen in a transverse section of the calyx of Magnolia grandiflora, where each of the three leaves embraces that within it. When the parts of a whorl are five, as occurs in many Dicotyledons, and Fig 194. Fig 195. FIG. 194. Diagram to illustrate imhricative or imbricated activation, In which the parts arc arranged in a spiral cycle, following the order indicated by the figures 1, 2, 3, 4, 5. FIG. 195. Diagram of a papilionaceous flower, showing vcxillary rcstivation 1 and 2, the alae or wings; 3, a part of the carina or keel; 4, the vexillum or stan dard, which, in place of being internal, as marked by the dotted line becomes external ; 5, the remaining part of the keel. The order of the cycle is indi cated by the figures. the imbrication is such that there are two parts external, two internal, and a fifth which partially covers one of the internal parts by its margin, and is in its turn partially covered by one of the external parts, the aestivation is quincuncial (fig. 193). This quincunx is common in the
corolla of Kosaceas. In fig. 194 a section is given of the
