Page:EB1911 - Volume 10.djvu/576

 in a withered form, as in some palms, Typha and Pothos. In grasses the outer scales or glumes of the spikelets are sterile bracts (fig. 5, gl); and in Cyperaceae bracts enclose the organs of reproduction. Bracts are frequently changed into complete leaves. This change is called phyllody of bracts, and is seen in species of Plantago, especially in the variety of Plantago media, called the rose-plantain in gardens, where the bracts become leafy and form a rosette round the flowering axis. Similar changes occur in Plantago major, P. lanceolata, Ajuga reptans, dandelion, daisy, dahlia and in umbelliferous plants. The conversion of bracts into stamens (staminody of bracts) has been observed in the case of Abies excelsa. A lengthening of the axis of the female strobilus of Coniferae is not of infrequent occurrence in Cryptomeria japonica, larch (Larix europaea), &c., and this is usually associated with a leaf-like condition of the bracts, and sometimes even with the development of leaf-bearing shoots in place of the scales.

The arrangement of the flowers on the axis, or the ramification of the floral axis, is called the inflorescence. The primary axis of the inflorescence is sometimes called the 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 off by it, they are called pedicels. A flower having a stalk is called pedunculate 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 the terms rachis, peduncle and pedicel.

The peduncle is 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 spinosum. When 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 or hyacinth, 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. 6). The floral axis sometimes 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. 7). The adhesion of the peduncles to the stem accounts for the extra-axillary position of flowers, as in many Solanaceae. When this union extends for a considerable 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 connexion. 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 peduncle, or the part on which the whorls of the flower are arranged, is called the thalamus, torus or receptacle.

There are two distinct types of inflorescence—one in which the flowers arise as lateral shoots from a primary axis, which goes on elongating, and the lateral shoots never exceed in their development the length of the primary axis beyond their point of origin. The flowers are thus always axillary.

Exceptions, such as in cruciferous plants, are due to the non-appearance of the bracts. In the other type the primary axis terminates in a single flower, but lateral axes are given off from the axils of the bracts, which again repeat the primary axis; the development of each lateral axis is stronger than that of the primary axis beyond its point of origin. The flowers produced in this inflorescence are thus terminal. The first kind of inflorescence is indeterminate, indefinite or axillary. Here the axis is either elongated,