STRUCTURE. 11 



always springing from the lower part or rhizome. It is 

 erect or oblique, straight or bending, ascending when it 

 gradually assumes an erect direction after being decum- 

 bent below, creeping when it roots at the joints, naked 

 when there are no leaves on the upper part, leafy when 

 the sheaths clothe it, round or compressed or angular, 

 tvjo-edged or four-cornered, knee-jointed {geniculate) 

 when bent suddenly at the joints, bulbiferous when en- 

 larged at the joints. The rachis is simple or branched, 

 smooth or rough, round, compressed or angular. 



The leaves of grasses are all linear in form, and have 

 parallel veins, in common with the monocotyledonous 

 group in general. They vary in comparative length and 

 breadth, some being sword-shaped, some strap-shaped, and 

 some awl-shaped. The apex in some is acute and taper- 

 ing, in some blunt. The sword-shaped leaf grows gradu- 

 ally narrowed till it ends in an acute apex. The strap- 

 shaped leaf has both sides parallel, not beginning to 

 taper till near the apex. The awl-shaped leaf is narrow, 

 generally grooved, and the edges rolled in so as to be like 

 a bristle, and very sharp-pointed. 



The surface of the leaves is channelled when the mid- 

 rib is very strongly developed, causing a ridge on the 

 under part of the leaf and a groove on the inner ; it is 

 nerved when the side-ribs are strongly marked ; and it is 

 characterized as flat when there are no furrows, or ribs, 

 or strongly developed markings ; some are smooth on the 

 surface, some downy, and some hairy. 



The margin of the leaf is plane, downy, hairy, or 

 saw-edged [serrate] as in the Pampas grass, where the 

 teeth are so sharp and strong as to inflict painful 

 wounds. 



The sheaths are continuous with the leaf; they em- 



