2o68 A TEXTBOOK OF THEORETICAL BOTANY 



Grass {Agropyron repens), Brome Grass {Bromiis mollis and 

 B. sterilis). Sheep's Fescue (Festuca ovitia), Cock's Foot [Dactylis 

 glomerata). Dog's Tail [Cynosurus cristatus), Quake Grass [Briza 

 media), Smooth Meadow Grass {Poa pratensis). 



2. Grasses common in marshes and damp places: Common Reed 



{Phragmites communis). Purple Mohnia {Molinia caerulea), Flote 

 Grass {Glyceria fluitans). 



3. Grasses common in woods: Millet Grass (Milium ejfiisum), Wood 



Melick (Melica uniflora), Wood Poa (Poa nemoralis). 



4. Grasses common on moors and heaths: Common Bent [Agrostis 



tenuis), Mat Grass (Nardus stricta). 



5. Grasses found on the sea-shore and dunes: Marram Grass (Ammo- 



phila arenaria), Lyme Grass (Elymtis arenarius). Cord Grass 

 [Spartina stricta and S. townsendii). 



The plants are nearly all herbaceous with the exception of the Bamboos. 

 The stems are generally hollow tubes, with enlarged nodes. The leaves 

 are alternate and generally arranged in two opposite orthostichies. They 

 consist of a long sheath, surrounding the stem, and a lamina, which is linear 

 and generally bears a ligule at the base. Many are annuals, but in perennial 

 species vegetative propagation is effected by rhizomes, or by tillering, i.e., 

 axillary branching, at the base of the tuft, the branches often rooting 

 independently. 



The inflorescence is complex and consists of groups of the individual 

 flowers in spikelets, which are themselves grouped together to form com- 

 pound inflorescences of various types. 



The spikelet consists of a short central axis, the rachilla, bearing a 

 number of scales closely arranged in two rows. The two basal scales are 

 barren, that is they bear no flowers in their axils, and they are termed the 



glumes. Above the glumes are a number of 

 bracts each subtending a flower. They are called 

 the outer paleae. The outer palea or lemma 

 sometimes bears a long process called the awn 

 or arista. The number of flowers in a spikelet 

 varies. There may be from one to five or more 

 perfect flowers, usually the lower ones, while the 

 upper flowers are often incomplete and sterile. 



The flower (Fig. 2006). The flowers them- 

 selves may be either hermaphrodite or unisexual. 

 In the latter condition in some instances, male 

 Fig. 2006. — Floral diagram flowers may be separated from the female flowers 



EkMelT'''''''' ^^^^"' ^"^ ""'ay even be grouped in separate inflores- 

 cences, as in Zea mais, where the male flowers 

 form a loose, terminal panicle, while the female inflorescences are borne 

 laterally in the axils of the foliage leaves, each consisting of a fleshy spadix 

 sheathed in bracts. 



