432 



BRITISH FLOWERING PLANTS 



and Fig. 345 of 



useful in these ways, but is not an even more important 



service that they tend to pre- 

 vent the seeds being eaten ? 



Fig. 346 gives a diagram 

 of a spikelet of Antho- 

 xanthum 

 Wheat. 



The flowers open only 

 once, generally in the morn- 

 ing, through the swelling 

 of the lodicules. As usual 

 in wind flowers the fila- 

 ments are very thin, so that 

 the anthers are easily shaken 

 by the wind. Some species 

 have cleistogamous flowers. 



FiQ. 346. — Diagram of a spikelet of rni n 1 1 



Anthoxanthum dissected ( x about -l-hc tlowers are generally 

 8), and showing— from below up- complete, but sometimes, as 



wards — 2 outer and 2 (awned) . -J^ . . _ ' . 



inner barren glumes, fertile glume m MaiZe, UniSeXUal. Ihe 



and pale, stamens, and pistil. leayCS COnsist of twO partS 

 There are no lodicules. i • i i 



— a sheath which encloses 

 and strengthens the stem, and a free blade (Fig. 347). 

 The sheath is generally split open on the side opposite 

 the blade. At the point where the 

 blade quits the sheath is a small, 

 scarious appendage known as the ligule. 

 Its probable use is to serve as a dam, 

 and prevent the rain which runs down 

 the blade from getting between the 

 sheath and the culm, and to turn the 

 little stream on each side down a 

 groove, and so to the exterior of the 

 sheath. Species which grow in the 

 shade of woods have thin flat leaves ; 

 those of moor and heath grasses are 

 thicker, stronger, setaceous, or rolled 

 in at the edges (Fig. 349). This is 

 efl^ected by " motorcells," which are thin-walled, vary in 

 turgescence, and are seated on each side of the mid-rib. 



Fig. 347. — Poa trivi- 

 alis, showing parts 

 of leaf. A, base of 

 blade ; B, ligule ; 

 C, upper part of 

 sheath ; D, culm. 

 X about 3. 



