10 



THE BLADE. 



the side oiDiaosite the blade, though exceptional cases are cited 

 where the sheaths are closed, as in Bromus (chess), Melica 

 (melic grass), and some others. The sheaths of the uiDper leaves- 

 of most grasses are split down to the node, but those of the lower 

 leaves in very many species are closed. In some cases the sheaths, 

 are closed at an early stage of development, l)nt later they are 

 split open jiart of the way down by the enlargement of the grow- 

 ing culm and the young leaves as they push upwards. This is*, 

 illustrated in Fig. 7. 



Fig. 7.— a, A thin cross section of a young leaf of Poa iiratcitxis witli the blade condu- 

 plicate, and the surrounding sheath closed ; b, a section still lower down, showing 

 three closed sheaths ; c, still lower down near a node, where Ave leaves have the 

 sheaths closed. 1x10.— (Sudworth.) 



At the upper end of the sheath there is often a membranous, 

 scale, tongue, or fringe, called the Ugule. The reader will con- 

 sult Fig. 51, and observe the ligule of a leaf of June grass. That 

 part of the leaf, which spreads away from the culm, is known 

 as the 



Blade or lamina^ and is usually sessile and slender, tapering to a 

 point. 



To the ordinary observer the blades of grasses seem to be very 

 nearly alike. Even Linnajus thought so, but to the botanist of 

 to-day they present very marked differences. 



The abortive leaves on root-stocks, generally consist mainly of 

 rudimentary sheaths. Commonly, all the leaves on a stem are 

 much alike, but in some cases the lower leaves are quite unlike 

 those above. I'he lower leaves of some species of Bambusa 

 (bamboo), Oryzopsis asperifoUa (mountain rice), Panicum 



