All our ordinary grasses except _Nardus_--where there is a simple straight hairy style--have two spreading feathery stigmatic plumes, which stand out right and left from between the paleæ when the pollen is flying about on the wind. (Fig. 33.) Much interesting speculation has been expended in attempting to explain the morphological or theoretical significance of the parts of the spikelet of a grass. If we project the various organs on a flat surface in the form of a plan, keeping their relative positions intact, we obtain a diagram such as that shown in Fig. 34. [Illustration: Fig. 34. Diagram of a spikelet of a grass. The two glumes--_g^1_ outer, _g^2_ inner--embrace four flowers, of which 1 is the lowermost and 4 the uppermost.] The comparison of numerous cases, and the study of the development of the parts on the microscopic growing point dissected out from young buds, have suggested that the inner and outer glumes are bracts, or covering leaves, at the base of the true spikelet. In like manner the two paleæ are bracteoles which subtend the flower proper. On this assumption they can be compared with the corresponding structures in other plants; whereas any attempt to compare the paleæ or glumes with the sepals and petals of ordinary flowers breaks down. A curious interest attaches to the awns so often found on the backs of paleæ, and especially to those where the (sub-terminal) awn springs from just below the bifid apex (e.g. _Avena_, &c.). Hackel showed by comparison with a rolled leaf attached to its sheath and ligule (e.g. _Psamma_) that such an awn as that of _Bromus Alopecurus_ attached to its palea stands in the relation of a leaf to its sheath, the part of the palea above the insertion corresponding to the ligule, the awn itself to the lamina, and the palea below its insertion to the sheath. This view is rendered the more probable by the anatomy of the awn and by the observations of Schmid, who has shown that the awns of cereals contain chlorophyll-tissue and a vascular bundle, and have stomata, and his experiments led him to conclude that in the young condition they transpire and assimilate, and probably even contribute to the nutrition of the ripening grain. When dry and mature the awns subserve biological functions of quite another kind, and as we shall see are of importance in the distribution and sowing of the grains. (Fig. 42.)