STRUCTURE, MORPHOLOGY, AND PHYSIOLOGY. 



of the latter (ligule) which is usually membranous, but 

 may be herbaceous at the sides. It originates from an 

 additional growth of the sheath upwards at the insertion 

 of the blade. If the 

 blade is narrower than 

 the sheath, then at 

 least the side portions 

 of the ligule are of the 

 same character as the 

 sheath, and are fur- 

 nished with fibro-vas- 

 cular bundles, while 

 the centre, upon which' 

 the blade rests ' while 

 in the bud, remains 

 membranous (see Fig. 

 3, B}. If the blade is 

 the same breadth as 

 the sheath, then the 

 entire ligule is mem- 

 branous (Fig. 3, A). 

 In the flowering glumes of many grasses Avena and 

 Bromus, for example whose blade has developed into 

 an awn (Fig. 3, 6 7 ),the ligular portion is much developed, 

 and the awn is then said to be on the back or dorsal (see 

 above). Flowering glumes with terminal awns have no 

 ligular portion ; there are also analogous cases in ordi- 

 nary leaves, for example in Panicum Crus-galli L. In 

 many grasses, especially in many of the Chloridece, the 

 ligule is transformed into a fine hairy fringe. The ligule 

 always embraces the culm very closely, and Schlechten- 

 dahl thought that its office was to keep rain or water 

 from getting between the sheath and culm. 



The Leaf-blade. The blade is usually elongated, nar- 

 row linear or linear-lanceolate, rarely, and only in tropical 

 species, ovate-lanceolate, elliptical, cordate or sagittate 

 (PJiyllorachis, etc.). In the bud the leaf is simply 

 folded (rarely plicate folded, as in Panicum plicatum and 

 related species) or rolled up from one side, the other 

 half being somewhat broader, and the sides by which 



FIG. 3. Point of separation of the sheath (s) 

 and blade (spr). A, in Dactijlis glomerata L. 

 B, in Ammophila arundinacea Host. I, Lig- 

 ule. C. Flowering glume of Bromus Alope- 

 curus Poir. 



