Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/65

Rh  Inflorescence.&mdash;This possesses an exceptional iirport- ance in grasses, since, their floral envelopes being much reduced and the sexual organs of very great uniformity, the characters employed for classification are mainly derived from the arrangement of the flowers and their investing bracts. The subject also presents unusual difficulties from the various interpretations which have been given to these glumaceous organs and the different terms employed for them by various writers. It may, however, be now con sidered as settled that the whole of the bodies known as glumes and palese, and distichously arranged externally to the flower, form no part of the floral envelopes, but are of the nature of bracts. These are so arranged round the small flowers as to form spikelets (locust), and each spikelet may contain one, two, three, or a greater number of flowers (in some species of Eragrostis nearly 60). The flowers are, as a rule, placed laterally on the axis (rachis) of the spikelet, but in uniflorous spikelets they appear to be terminal, and are probably really so in Anthoxanthum (fig. 9, 2) and in two anomalous genera, Anomochloa and Streptochcete. In immediate relation with the flower itself, and often entirely concealing it, is the palea or pale (&quot; upper pale &quot; of most systematic agrostologists ; &quot; paleola interior,&quot; Dumortier; &quot;spathella,&quot; Doll). This organ (fig. 3, 1) is peculiar to grasses among Ghimiferce, and is almost always present, certain Oryzece and Phalaridece being the only exceptions. It is of thin membranous consistence, usually obtuse, often bifid, and possesses no central rib or nerve, but is furnished with two lateral ones, one on either side ; the margins are frequently folded in at the ribs, which thus become placed at the sharp angles. This structure points to the fusion of two organs, and the pale was by R. Brown considered to represent two portions soldered together of a trimerous perianth-whorl, the third portion being the &quot; lower pale,&quot; to be immediately mentioned. By Bentham the homology of the organ is suggested to be with the two bracteoles found in Hypolytrum pungens and Platylepis, and with the perigynium of the female flower of Car ex in Cyperacece. It is rarely (Triachyrum, Diachy- rium) found split into two separate organs. The flower with its pale is sessile, and is placed in the axil of another bract in such a way that the pale is exactly opposed to it, though at a slightly higher level. It is this second bract which has been generally called by systemat- ists the &quot;lower pale,&quot; and with the &quot;upper pale&quot; con sidered to form an outer floral envelope (&quot; calyx,&quot; Jussieu ; &quot; perianthium,&quot; Brown ; &quot; stragulum,&quot; Palisot de Beauvois; &quot; glumella,&quot; Dumortier). In the writings of most botanists even though this view is not held, yet, where the term &quot; flower &quot; is employed, it includes these organs. It is, how ever, certain that the two bracts are on different axes, one secondary to the other, and cannot therefore be parts of one whorl of organs. This was made out from the study of so- called &quot;viviparous&quot; grasses, in which the lower pales become transformed into ordinary foliage leaves, first by Von Mohl in 1845, and more clearly by Germain de St Pierre in 1852, who terms the lower pale the &quot;glume fertile.&quot; Doll and Bentham have also independently ar rived at the same result, and the latter in 1858 first published the terminology here adopted, and used for the same organ the name flowering glume. The two bracts are usually quite unlike one another, but in some genera (e.g., most Festucacece) they are considerably similar in shape and appearance. The flowering glume has generally a more or less boat- shaped form, is of firm consistence, and possesses a well- marked central midrib and frequently several lateral ones. The midrib in a large proportion of genera extends into an appendage termed the awn (fig. 10, 2), and the lateral veins more rarely extend beyond the glume as sharp points (e.g. t Pappophorum). The form of the flowering-glume is very various, this organ being plastic and extensively modified in different genera. In Leptaspis it is formed into a closed cavity by the union of its edges, and encloses the flower, the styles projecting through the pervious summit. Valu able characters are obtained from the awn. This presents itself variously developed from a mere subulate point to an organ several inches in length, and when complete (as in Andropogone(, Avenece, and Stipece) consists of two well- marked portions, a lower twisted part and a terminal straight portion, usually set in at an angle with the former sometimes trifid and occasionally beautifully feathery. The lower part is most often suppressed, and in the large group of the Panicece awns of any sort are very rarely seen. The awn may be either terminal or may come off from the back of the flowering-glume, and Duval Jouve s observations have shown that it represents the blade of the leaf of which the portion of the flowering-glume below its origin is the sheath ; the twisted part (so often suppressed) cor responds with the petiole, and the portion of the glume extending beyond the origin of the awn (very long in some species, e.g., of Danthonia] with the ligule of the developed foliage-leaf. When terminal the awn Las three fibro-vascular bundles, when dorsal only one ; it is covered with stomate-bearing epidermis. The flower with its palea is thus sessile in the axil of a floriferous glume, and in a few grasses (Leersia (fig. 2), Coleanthus, Nardus] the spikelet consists of nothing more, but usually (even in uniflorous spikelets) other glumes are present. Of these the two placed distichously opposite each other at the base of the spikelet never bear any flower in their axils, and are called the basal or empty glumes (fig. 10, 1). They are the &quot;glumes&quot; of most writers (&quot;palese&quot; of Dumortier), and together form what was called the &quot;gluma&quot; by R. Brown (&quot; tegmen,&quot; Palisot de Beauvois). They rarely differ much from one another-, but one may be smaller or quite absent (Panicum (fig. 8, 2), Vulpia,

&mdash;Spikelet of Leersia.

Paspalum, Lolium), or both be altogether suppressed, as above noticed. They are commonly firm and strong, often enclose the spikelet, and are rarely provided with long points or imperfect awns. Generally speaking they do not share in the special modifications of the flower ing glumes, and but rarely themselves undergo modifica tion, chiefly in hardening of portions (Sclerachne, Manisiiris, Antephora, Peltopkorum), so as to afford greater protection to the flowers or fruit. But it is usual to find, besides the basal glumes, a few other empty ones, and these are in two- or more-flowered spikelets (fig. 11, 2) at the extremity (numerous in Lophatherum), or in uniflorous ones (fig. 8, 2) below, interposed between the floral glume and the basal pair. Descriptive writers have been accustomed to call these empty glumes &quot; barren &quot; or &quot; neutral flowers,&quot; a misleading use of terms. The axis of the spikelet, when short and rounded, has been termed the calhis, when long the rachilhis. It is fre quently jointed and breaks up into articulations above each flower. Tufts or borders of hairs are frequently present (Calamagrostis, Phragmites, Andropogon), often so long as to surround and conceal the flowers. The axis is often continued beyond the last flower or glume as a bristle or stalk.

Involucres or organs outside the spikelets are not unfre- quent, the morphology of which is various. Thus in Setaria, Pennisetum, &c., the one or more circles of simple or feathery hairs represent abortive branches of the inflor escence ; in Cenchrus these become consolidated, and the 