186 



KNOWLEDGE 



[October 1, 1892. 



grass (Phleum pratenae), to a compound loose raceme or 

 panicle of many-flowered spikes, as in Aira rusjiitasd, Amin 

 (the oat), and lluUus Idimtiis (the Yorkshire fog). Fig. V. 

 represents the panicle of Aim cirxjiitiiK,/, Fig. IV. a spikelet 

 oilliilius hi nut i(s, a.nd Fig. III. that of the perennial rye-grass 

 (LoUiiin pcrenne), whose inflorescence is a spike of many- 

 flowered spikelets. 



We will now examine the two spikelets figured. At 

 Fig. IV., st is the short stalk of the spikelet, by which it 

 is fastened to a lateral branch of the main axis of the 

 inflorescence. It bears first two leaves {tj. //.), called the 

 glnmes; in the young condition these enclose the flowers 

 borne on its upper portion. One of them is furnished with 

 an arista or awn {n). There are two flowers in this spikelet. 

 Each arises in the axil of a leaf called the outer palea 

 (0. jj.), which is morphologically a bract, as the definition 

 of a bract is " a leaf in the axil of which a single flower 

 arises." In dicotyledons — for instance, in Leguminosne 

 — two small greenish bodies may sometimes be observed, 

 situated laterally on the peduncle or flower stalk, 

 and in monocotyledons one placed opposite the bract, their 

 number thus coinciding with that of the cotyledons. These 

 structures are called prophylls or bracteoles. What is 

 commonly called the inner palea ( /. p.)oi the graminaceous 

 flower is thus a prophyll. The outer palea often bears an 

 awn. In fjalrus lanatm the outer palea* of the upper 

 flower only is furnished with this appendage, and it arises 

 from the middle of the back. 



The structure of the flower is peculiar, and departs rhnch 

 from the typical monocotyledouous type. In the Liliacene 

 (lily order), which may be selected as the typical form of 



this class, there are five whorls 

 of floral organs — the perianth 

 (re/it, around, and avSoc, a 

 flower) or floral envelope, two 

 whorls of three members each ; 

 the andrircium {avrip, a man, 

 and o'lKOj, a house), two 

 whorls of three stamens each ; 

 and the gynoi'cium [yuvq, a 

 woman) of three carpels united 

 together. The members of 

 the successive whorls alter- 

 nate with one another, and 

 the odd sepal is anterior, that 

 is, it is situated next the 

 observer who holds the flower 

 between himself and the axis 

 on which it arises. This ar- 

 rangement is seen in Fig. II. 

 1. In the Liliacew there is a 

 conspicuous perianth denoting 

 that the flowers of that order 

 are indebted to insects for per- 

 forming the work of cross- 

 fertilization. The flowers of 

 the Gramineffi are wind pol- 

 linated, or anemophilous 

 (avE/y.of, the wind, and <^iXi:a, 

 to love), and as is usual iu 

 is inconspicuous, being here 

 represented by insignificant, generally microscopical, scales, 

 usually two in number, termed lodicules (Fig. II., /). 

 These swell and push the bract outwards when the stamens 

 and stigmas are ripe, and thus expose the organs of repi-o- 



of 



axis ; ■ 

 , stamen 



the 



Fig. II. 



1. Floral diagram 

 Liliaee.T ; o., iloral 

 sepals ; p., petals ; st-. 

 r., carpels. 



2. Ditto of Bamboo (Bnm- 

 hiisa ariniillnrtcea); /..lodicules ; 

 o. p., outer palea ; /. y^., intu-r 

 )i.ilca. 



3. Ditto of Eieo (Ori/za) ; .,/., 

 glume. 



4. Ditto of Oat {.i i-i'iia satira). 



such cases the perianth 



one m 



These are thus 



* The outer palea lias also been termed the flowering glume, anj 

 the glumes the outer glumes. As a rule, the latter organs do not bear 

 flowers in tjjeir axils. 



duction for the purpose of pollination. The two lodicules 

 alternate in position with the outer palea ; if a third one is 

 present it stands opposite the inner palea. The stamens 

 (Figs. III. and IV. '(») are generally three in number. 

 Their very fine filaments appear to be fastened to 

 the back of the anthers — versatile condition — owing to 

 the downward growth of the anther lobes. The odd 

 stamen is anterior ; it is thus the inner whorl that 

 is undeveloped. The two carpels (Figs. II. and IV. 

 c) are united together or synearpous ( o-uv, and Kainto;, 

 a fruiti. The two large feathery stigmas (Fig. III., -s-f) 

 are admirably suited to intercept the pollen grains wafted 

 thither by the wind. 



A nearer approach to the structure of the typical 

 monocotyledonnus flower is made by that of the bamboo 

 (Fig. II. 2), which possesses six stamens and carpels, 

 but only three instead of six perianth segments. Six 

 stamens are also present in some half dozen other genera, 

 while in Ulicrolceno, Ti'trarrliena, and AnomdrMcti there are 

 four. But two are iound in Antho.mnthum — Anthoxdntluini 

 iiihiratum is the sweet-scented vernal grass — and 

 Uniola and Monandraia (Fig. IIa. 

 more anomalous in form 

 than Lolium and Holcus. 

 Holcus, however, presents 

 the anomaly of having 

 hermaphrodite and male 

 flowers on the same plant, 

 a condition known as 

 andro-monrecious (f/.oyos, 

 one) — see Fig. IV., where 

 the lower flower of the 

 spikelet is hermaphrodite, 

 the upper male. Andro- 

 monnpcism is also found 

 in some members of the 

 Fescue tribe. The rice 

 {Ori/:ii) has six stamens 

 like the bamboo, but has 

 only two carpels. In the 

 maize [Xca Mais) the 

 flowers are male or female, 

 and both kinds are found 

 forming female spikes and 

 a male panicle on the one 

 plant. The maize is thus 

 monfpcious. A curious 

 change occurs in the fe- 

 male flower of .Tob's tears 

 (Coi.r liicliri/iiiii), a native 

 of tropical Asia. The 

 outer glume becomes bony 

 and completely invests the 

 mature spikelet, making the whole appear like a seed with 

 a very hard case. The diagram of this anomalous form 

 (Fig. IL\., 0) shows the position of the parts. 



Fig. IIa., 7, is a diagram of a spikelet of the oat (Arena). 



The fruit is usually composed of two carpels, which 

 enclose a single cavity containing a single ovule. It is 

 generally the case that the seed or seeds are free from the 

 wall of the ovary, but in grasses they are united together, 

 and the resultant dry fruit, which does not open to allow 

 its seeds to escape, is called a ((iriiojmi.s. A longitudinal 

 section of the maize fruit taken through the centre of the 

 embryo exhibits the parts shown in Fig. IV. The pericarp 

 (iTspi, around, and Kapvos, a fruit) is formed from the 

 united nucellus or wall of the ovule, and true pericarp or 

 ovarian wall. The embryo occupies a very small portion 

 of the cavity of the ovule, the remainder of the embryo 



Fig. IIa. 



5. Floral diagram of Monayidrain 

 fllnvca. 



(>. IMtto of Job's Tears (Coix 

 lachripnn) ; //, outer glume, forming 

 bonv involucre investing the spike- 

 let ; //', inner glume. (After Le 

 Maont and Decaisne). 



7. Spikelet of Oat ; a. f.. aliorted 

 llower. 



