MONOCOTYLEDONS. 305 



flume instead of two, while in Sweet Vernal Grass there are four, 

 he outer glumes are rarely awned (Nardus, Phleum, Couch-grass) ; 

 in Barley they are narrow, pointed, and stiff, but in most Grasses they 

 are boat-like. The flowering-glume and the palea are often awned, 

 especially the former (Oat-grass, False Oat, Barley, Bromes, Darnel, 

 etc. ) ; the palea is usually smaller and more delicate than the flowering- 

 glume, and it usually has two side-veins but no midrib. 



The awn carried by the flowering-glume (or by the empty glumes, 

 or by all the glumes) grows from the midrib and may be terminal or 

 inserted on the back of the glume. Awns act as a protection against 

 birds and browsing animals ; in some cases they aid in dispersal by 

 wind or by animals. Besides these uses the awn has a vein, green 

 tissue, and stomates, so that it can assimilate and transpire, and it 

 doubtless helps in the nutrition of the developing grain. The awn 

 probably corresponds to the reduced leaf-blade, the basal part of the 

 glume to the leaf -sheath, and the free portion beyond the awn to the 

 ligule of a leaf. The two lodicules (absent in Sweet Vernal Grass, 

 Nardus, Foxtail, etc.) of most Grasses (three or even more occur in 

 some foreign Grasses, e.g. Bamboo) are probably mere extra scales, 

 not representing a perianth. 



In all British Grasses there are three stamens (except Sweet Vernal 

 Grass, which has two), and the pistil has two feathery styles, right 

 and left (except Nardus, which has a single style). In some foreign 

 Grasses there is only one stamen, in others six, while some have as 

 many as forty ; while there may be three styles (some Bamboos) or a 

 single long style (e.g. Maize). Hence the typical Grass flower consists 

 simply of two stigmas and a single carpel, with no perianth. The 

 "styles" do not correspond to two carpels in this family. The lodi- 

 cules, when present, are said to swell up and push apart the scales 

 enclosing the flower, so that the stamens and styles may more easily 

 project from between them. 



In most Grasses the pollen is shed before the stigmas are ready to 

 receive pollen, but in some Grasses P. g. Sweet Vernal Grass, Foxtail 

 the opposite is the case, i.e. the flower is protogynous. In some 

 foreign Grasses the flowers are unisexual e.g. Maize, where the 

 feather-like male inflorescences occupy the top of the plant, while the 

 female ones (" cobs") are near the base. 



In most cases there is a chance of cross-pollination, but most cereals 

 are largely self-pollinated ; in Rye the flowering-glume and palea do 

 not separate at all, hence the flowers are self-pollinated. Grasses are 

 wind-pollinated (what are their adaptations for wind-pollination?), 

 but some, e.g. Sweet Vernal Grass, are frequently visited by flies. 



In most British Grasses the grain remains within the flowering- 

 glume and palea, as in Oat, and becomes detached along with these 

 and the part of the axis of the spikelet which bears them. There are 

 several adaptations for dispersal of the grains by wind or by animals. 

 In Hair-grass (Aira) there are silky hairs below the flowering-glume, 

 and in many cases the glumes expand and act as wings ; some Grasses 

 have small light grains, easily carried by the wind. The awns, 

 especially when bent, catch on to animals ; a familiar example is seen 



S. B 20 



