Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/131

Rh PEDUNCLE.] BOTANY 121 The arrangement of the flowers on the axis, or the ramification of the floral axis, is called inflorescence or anthotaxis. The primary axis of inflorescence is some times called rachis ; its branches, whether terminal or lateral, which form the stalks supporting flowers or clusters of flowers, are peduncles, and if small branches are given oil by it, they are called pedicels. A flower having a stalk is called 2^dunculate or pedicellate; one having no stalk is sessile. In describing a branching inflorescence, it is common to speak of the rachis as the primary floral axis, its branches as the secondary floral axes, their divisions as the tertiary floral axes, and so on ; thus avoiding any confusion that might arise from the use of tbe terms rachis } peduncle, and pedicel. Fig. 150. Fig. 149. FIG. 149.- Spikelet of Oat (Arena satiia) laid open, showing the bracts gl, gJ, which arc denominated empty glumes ; pe, the outer pale or ghnnellule (floral plume), with a dorsal awn a; pi, the inner pale; fs, an abortive flower. FIG. 150. Peduncle, a, of Fig (Ficus Carica), ending in a hollow receptacle 6, enclosing numerous male and female flowers. The peduncle may be cylindrical, compressed, or grooved ; simple, bearing a single flower, as in Primrose ; or branched, as in London-pride. It is sometimes succulent, as in the Cashew, in which it forms the large coloured expansion supporting the nut; spiral, as in Cyclamen and Vallisneria ; or spiny, as in Alyssum spiuosum. In some Rushes there is a green terete, and sometimes spiral, floral axis. Some times the peduncle proceeds from radical leaves, that is, from an axis which is so shortened as to bring the leaves close together in the form of a cluster, as in the Primrose, Auricula, Hyacinth, &c. In such cases it is termed a scape. The floral axis may be shortened, assuming a flattened, convex, or concave form, and bearing numerous flowers, as in the Artichoke, Daisy, and Fig (fig. 150). In these cases it is called a receptacle or phorantkium or clinanthium. The floral axis sometimes assumes a leaf-like or phylloid appearance, bearing numerous flowers at its margin, as in Xylophylla longifolia and in Ruscus ; or it appears as if formed by several peduncles united together, constituting a fasciated axis, as in the Cockscomb, in which the flowers form a peculiar crest at the apex of the flattened peduncles. Adhesions occasionally take place between the peduncle and the bracts or leaves of the plant, as in the Lime-tree (fig. 151), Helwingia, Chailletia, several species of Hibiscus, and Zostera. The adhesion of the peduncles to the stem accounts for the extra-axillary position of flowers, as in many Solanacece. When this union extends for a consider able length along the stem, several leaves may be interposed between the part where the peduncle becomes free and the leaf whence it originated, and it may be difficult to trace the connection. 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. The termination of the Plate II. Fig. 152. ?. 151. FIG. 151. Leaf and flowering branch of the Lime-tree (Tilia). The bract 6 is adherent to the peduncle or flower-stalk. The flowers are arranged in a corym bose cyme. FIG. 152. The calyx and beak -like process of Geranium, with the parts of the pistil (the carpels) curled upwards, so as to scatter the seed, a, the extremity of the rostrum or beak, whence the name crane s bill is derived ; 6, the carpels curled up by means of the styles which are attached to the beak ; c, the calyx. peduncle, or the part on which the whorls of the flower are arranged, is called the thalamus or torus. The term receptacle is also sometimes ap plied to this, whether expanded and bearing several flowers, or narrowed so as to bear one. It may be considered as the growing point of the axis, which usually is arrested by the production of the flowers, but which sometimes becomes enlarged and expanded. Thus, in the Geranium (fig. 152) it is prolonged beyond the flower in the form of a beak (rostrate) ; in the Arum (fig. 153) it is a club- shaped fleshy column ; in the Strawberry (fig. 154) it becomes a conical succulent mass, on which the seed-vessels are placed; while in Nelumbium it forms a trun cated tabular top-like expansion (turbinate), enveloping the seed- vessels. The margins of the re ceptacle may grow up whilst the Fig. 153. centre remains depressed, and thus FIG iss.-Spadix of Cuckow-pint ,, . (Arum maculatum), consisting a Concave torUS IS formed, as in of numerous male flowers 6, the Rose (fig. 155). In some mon strous flowers of the Rose and Geum it is prolonged as a branch bearine; leaves. Peduncles and Fig. 155. female a, and abortive flowers c, sessile on a succulent raohis, and enclosed in a spathe. which in the figure has been removed. The rachis ends in a succulent club-shaped mass of cellular tis sue, d. pedicels sometimes become re- FIG. 154. Fruit of the strawberry d +1 (Fragaria yesca), consisting of markably elongated, elongation of the flower-stalks sometimes alters the general char acter of the inflorescence. We an enlarged succulent prolonga tion of the receptacle,- bearing on its surface numerous carpels, which are often erroneously called seeds. The calyx is seen at the lower part. occasionally observe the heads of Fig. 155 The fruit of the Rose n _* A i_- inn..-!.- cut vertically. The receptacle re lines the interior of the calyx co, and the carpels with their ovaries ov and styles sty are attached to it. The stamens and petals are seen at the upper part, , attached to the calyx. Inflores cence. flowers of the common White Clover becoming racemose by the lengthening of the flower-stalks. Before proceeding to an ex amination of the parts of the flower-bud, we will consider the various modes of arrange ment of the flowers upon the axis, or the inflorescence. IV. 16