GRASSES 



361 



weight ami kind of material. The sterns of grasses 

 are further strengthened ly impregnation with 

 -ili.-a. Annual grasses have tufted, fibrous roots, 

 I mi most graces [lerennate by means of noli- 1 under- 

 ground steins ( rhizomes ), from the nodes of which 

 roots are developed ; roots also grow freely from 

 the lower nodes of the aerial steins of all grasses. 

 The fimrers are mostly hermaphrodite, as in barley 

 ami oats; maize and a few outers an- monoeciotM; 

 ami some of the fescue tribe have the lower 

 hiTinaphrodite and the upper male. Each flower 

 is enclosed by two bracts (paleie), which are the 

 hoiiiologues of the two spathe-like bracts in the In 

 llon'scences (q.v. ) of Iridaceje. The posterior bract 

 is two-nerved, indicating its two-fold nature, and 

 often clasps the fruit when mature ; the anterior 

 ( ' flowering glume ') surrounds both, and sometimes 

 bears an Awn (q.v.), as in barley. A number of 

 flowers may be crowded together to form a spikelet ; 

 and, further, a number of such spikelets may be at- 

 tached by stalks to 

 a central axis, form- 



ing a raceme, as 

 in Melica nutans 

 ( fig. 2 ) ; when the 

 raceme is loosely 

 branched, the inflo- 

 rescence becomes a 

 panicle, as in Oats 

 ( q.v.); or the spike- 



. mft y ke 8e8s ^ e 

 on a central axis, 

 forming a com- 

 pound spike, as in 

 ryegrass (Loliuin). 

 The spike may be 

 looked on as a re- 

 duced raceme or 

 panicle, in which 

 the stalks of the 

 epikelets have not been developed ; each spikelet 

 n>ay again be reduced to a single flower, and then 

 a simple spike like that of mat-grass (Nardus 

 strii-t/t ) is the result. Beneath the lowest flowers 

 of many spikelets there are two bracts ( glumes ) 

 which may or may not bear barren flowers in their 

 uxils. There is no perianth such as is found in 

 most insect-pollinated flowers. Grass flowers are 

 wind -pollinated and generally inconspicuous; in 

 some, however, there are two or rarely three scales 

 (lodicules) within the flower bracts; and these, 

 from their position and relation to the other parts 

 of the flower, may be regarded as segments of a 



Fig. 2. 



A. Mtlica nutans; inflorescence a 

 raceme of spikelets. B, Lolium 

 perenne; a compound spike. C, 

 Nardus stricta; spikelets reduced 

 to one flower each. 



. a 



A. floral diagram of Bambusa (for explanation, see article 

 FLOWBR): a, stigma; b, ovary; c, stamen; d, lodlcule ; e, 

 Inner bract ; /, outer bract ; g, stem. B, Avena : fc, glume ; 

 stamens reduced to three. C, Coleanthns : lodicuto frwant- 

 ing ; two stamens. D, Monaudraira : one stamen. 



rudimentary perianth. These scales, becoming 

 turgid at the period of sexual maturity, press the 

 anterior bract outwards, and expose stigmas and 

 stamens for pollination. Should wet weather occur 

 when this stage is reached the powdery pollen may 

 become clogged and kept from being blown about ; 



thus preventing fertilisation and the opportunity 

 of producing seed. 



Stamen* vary from six or more to one ; in British 

 grasses usually three, but three to one in the 

 fescue tribe. The slender filament* are inserted 

 at the bases of the anthers, but the anther lobe* 

 grow downwards below tin- point of insertion, and 

 the anthers appear to be, but are not, versatile. 

 The ovary is one-celled ; there are three or two 

 st\l's, with long and hairy, or short and feathery 

 stigmas, which are thus enabled to catch the winu- 

 borne pollen. The fruit is one-seeded (caryoptit) ; 

 the seed is adherent to the pericarp. The embri/o 

 by the great development of the farinaceous endo- 

 sperm is dis- 

 placed to one 

 side at the 

 base of the 

 latter, its sur- 

 face of con- 

 tact being 

 confined to 

 that of a 

 large process 

 of disputed 

 homology, 

 the scutel- 

 lum. When 

 a grain of 

 or 



Fig. 4. 



A, grain of wheat in vertical section : o, 

 pericarp ; b, endosperm ; c, sfiitelluni ; d, 

 young stem and leaves (plumule); e, first 

 root (radicle). B, grain of wheat after 

 germination has begun : /, secondary 

 roots. 



wheat 

 other grass 

 begins to ger- 

 minate, the 

 scu tellum 

 acts as a pla- 



cental surface to the embryo, digesting the sub- 

 stance of the endosperm, and passing it on in a 

 soluble state to the embryo, which soon begins 

 to develop roots and leaves. When all the endo- 

 sperm has been used up the seedling grass has put 

 forth roots enough to draw a sufficient supply of 

 sap from the soil, and green leaves to transform 

 the sap into food materials for the tissues of the 

 plant. The scutella of grains may be compared to 

 the suckers (haustoria) of mistletoe, for it is by 

 means of suckers that plant parasites fix upon, and 

 draw sap from, their hosts. 



Classification. The order is divided into two 

 divisions, the divisions into tribes, genera, and 

 species. The genera are omitted here, and only 

 trie better-known species are given as examples. 

 ( a ) PaniceoB. Spikelets articulate with the pedicels 

 below the lowest glume, with a single terminal fer- 

 tile flower, while the lower inferior is male or sterile. 



Tribe. Example*. 



PANICK. Panicum ; Setaria. 



MAYDE*. Job's Tears (Coix ) : Maize (Zea). 



OKYZE.E. Rice (Oryza) ; Cut Grass (Leersia). 



TUI-;-IT.I.INI:.K Arundinella. 



Xi i YS 11 :.-: Tragus. 



ANDROPOGONR*. . .Sugar-cane (Saccharum); Dam (Andro- 

 pogon); Millet (Sorghum). 



(6) Poacece Spikelets usually articulated above 



the lowest glume, 1- or many* flowered ; male or 

 imperfect flower above the fertile ones. 



Tribe. Example*. 



PHALARIDMS. Reed Canary Grass ( Phalaris) : Sweet Yernal 



Grass (Anthoxanthuni); Fox-tail Grass 



(Alopecurus). 



AOROOTIDEA Millet Grass (Miliuin): Timothy Gratt 



(Phleum); Bent (Agrostis). 

 AVENE.*:. Hair Grasn (Aira); Soft Grass (Holcus); 



Oats ( Avena \ 



CHLORIDES. Dog's-tooth Grass (Cynodon) ; Eleusine. 



FEUTUCE* Reed ( Phragmites ) : Dog's-tail Grass (Cyno- 



surus); Cock's-foot Grass (Dactylis); 



Melic Grass (Melica): Quaking Grass 



(Briza): Poa : Fescue; Bromus. 

 HORDKA. Rye (Seeale); Ryemss (Lolium); "Wheat 



(Triticum): Barley (Hordeum); Mat 



Grass (Nardus). 

 13 AMBCSXX. Bambusa ; Arnndi naria. 



