Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/141

Rh CALYX.] BOTANY 131 bud of Antirrhinum majus, showing the imbricate spira arrangement. In this case it will be seen that the pan marked 5 has, by a slight change in position, become overlapped by 1. This variety of imbricate aestivation ha been termed cochlcar. In flowers, such as those of the Pea (fig. 187), one of the parts, the vcxillum, is often large and folded over the others, giving rise to vexillary wstiva tion (fig. 195), or the carina may perform a similar office and then the aestivation is carinal, as in the Judas-tree (Cercis Siliquastrum). The parts of the several verticils often differ in their mode of aestivation. Thus, ii: Malvaceae the corolla is contortive and the calyx valvate or reduplicate ; in St Jolm s-wort the calyx is imbricate and the corolla contortive. In Convolvulaceae, while the corolla is twisted, and has its parts arranged in a circle the calyx is imbricate, and exhibits a spiral arrangement In Guazuma the calyx is valvate, and the corolla indupli- cate. The circular aestivation is generally associated with a regular calyx and corolla, while the spiral aestivations are connected with irregular as well as with regular forms I. PROTECTIVE ORGANS. 1. Calyx. The calyx is the external envelope of the flower, anci consists of verticillatc leaves, called sepals, foliola, or pliylla. These calycine leaves are sometimes separate from each other, at other times they are united, to a greater or les extent ; in the former case, the calyx is dialysepaloiis 01 eleutherosepalous, polysejxdous or polyphylltms, or apo- sepalous ; in the latter, gamosepalous or gamojihyttous, mono- sepalous or monophyllous, or synsepalous. The division of the calyx present usually all the characters of leaves, and in some cases of monstrosity they are converted into the ordinary leaves of the plant. Their structure consists of cellular tissue or parenchyma, traversed by vascular bundles, in the form of ribs and veins, containing spiral vessels, which can be unrolled, delicate woody fibres, and other vessels, the whole being enclosed in an epidermal covering, having stomata and often hairs on its outer .surface, which corresponds to the under side of the leaf. In the great divisions of the vegetable kingdom the vena tion of the calyx is similar to that of the leaves, parallel in Monocotyledons, reticulated in Dicotyledons. The leaves of the calyx are usually entire, but occasionally they are cut in various ways, as in the Rose, and they are some times hooked at the margin, as in Rumex uncatus. It is rare to find the leaves of the calyx stalked. They are usually sessile leaves, in which the vaginal portion is only slightly developed, and frequently the laminar part is alone present. Sepals are generally of a more or less oval, elliptical, or oblong form, with their apices either blunt or acute. In their direction they are erect or reflexed (with their apices downwards), spreading outwards (divergent or patulous), or arched inwards (connivent). They are usually of a greenish colour, and are called folia ceo us or herbaceous; but sometimes they are coloured, as in the Fuchsia, Troprcolum, Globe-flower, and Pomegranate, and are then called petaloid. Whatever be its colour, the external envelope of the flower must be considered as the calyx. The nature of the hairs on the calyx gives rise to terms similar to those already mentioned as applied to the surfaces of other parts of plants. The vascular bundles sometimes form a prominent rib, which indicates the middle of the sepal ; at other times they form several ribs. The venation is useful as pointing out the number of leaves which con stitute a gamosepalous calyx. In a polysepalous calyx the number of the parts is marked by Greek numerals prefixed. Thus, a calyx which has three sepals is Irisepalous; one with five sepals is pentasepalous or penlapliyllous. The sepals occasionally are of different forms and sizes. In Aconite one of them is shaped like a helmet, and has been called galeate. In a gamosepalous calyx the sepals are united in various ways, sometimes very slightly, and their number is marked by the divisions at the apex. These divisions either are simple projections in the form of acute or obtuse teeth; or they extend down the calyx as fissures about half way, the calyx being triftd (three-cleft), quinquefid (five- cleft), (fig. 196), &c., according to their number ; or they reach to near the base in the form of partitions, the calyx being tripartite, quadripartite, quinquepartite, &c. The union of the parts may be complete, and the calyx may bo quite entire or truncate, as in some Correas, the venation being the chief indication of the different parts. The cohesion is sometimes irregular, some parts uniting to a greater extent than others ; thus a two-lipped or labiate calyx is formed, which, when the upper or posterior lip is arched, becomes ringent. The upper lip is often composed of three parts, which are thus posterior or next the axis, while the lower has two, which are anterior. The part formed by the union of the sepals is called the tube of the calyx ; the portion where the sepals are free is the limb. Occasionally, certain parts of the sepals undergo marked enlargement. In the Violet the calycine segments (ladnice) are prolonged downwards beyond their insertions, and in the Indian Cress (Tropaeolum) this prolongation is in the form of a spur (calcar), formed by three sepals ; in Delphinium it is formed by one. When one or more sepals are thus enlarged, the calyx is calcarate or spurred. In Pelargonium the spur from one of the sepals is adherent to the flower-stalk. When an epicalyx is present, as in the Mallow order, the flower appears to be provided with a Plate III. double calyx, and has been denominated caliculate. De generations take place in the calyx, so that it becomes dry, scaly, and giumaceous (like the glumes of grasses), as in the Rush tribe ; hairy, as in Composites ; or a mere rim, as in Plate IX. some Umbelliferae and Acanthaceae, and in Madder (Rubia Plate VII. tinctorum, fig. 198), when it is called obsolete or margmate. In Diplolaena it is reduced to five scales. In Composite, Fig. 197. Fi&quot; 200. Fifl. 19C. Gamoscpnlous five-toothed (quinque-dentatc) calyx of Campion (Lychnis), IG. 197. -Feathery pappus attached to the fruit of Salsafy (Trayopogon poiri folitis) The calyx adheres to the fruit, and its limb is pappose. IG. 198. Calyx of Madder (Rubia), adherent to the pistil, its limb appearing in the form of a rim. The calyx is called obsolete. FIG. 199. Caducous calyx of Poppy (Paparer). It is composed of two sepa.s, which full off before the petals expand. G 200. Bladder-like calyx of the Winter Cherry (Physalis Alkekengf), .aid open to show the mode in which it surrounds the fruit without adhering to it. The calyx is persistent, bu ./ not adherent. It enlarges after the flower withers, and is called accrescent. Dipsacace*, and Valerianaceae, the calyx is attached to the &amp;gt;istil, and its limb is developed in the form of hairs called xippns (fig. 197). This pappus is either simple (pilose) or