vi] MORPHOLOGY OF AWN 95 
at the base of the true spikelet. In like manner the two 
pales 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 palez 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 pale, 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 msertion 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 con- 
clude 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.) 
Returning to the floral diagram, we see that the two 
lodicules, the three stamens and the ovary still remain to 
