302 



MONOCOTYLEDONS. 



to be a regular crop if the rainfall exceeds about 33 inches 

 a year, and if the average July temperature is below about 

 13 C. On upland farms the chief cereal crop is Oat, which 

 is cultivated in Europe to latitude 69 K 



The ears of Oat are not arranged in a close spike as in 

 Wheat, but in a loosely branching system ("panicle"), in 

 which the main axis gives off branches, which may again 

 branch, each branch ending in an ear, which hangs down- 

 wards. 



Examine an ear and compare its structure with that of 

 Wheat. Note the two large boat-like outer glumes, enclosing 

 (usually) three pairs of smaller scales (each pair = a flowering- 

 glume and a palea, as in Wheat), but usually only the two 

 lower pairs contain a flower, the small uppermost pair enclos- 



GLUME 



PALEA 



OVARY 

 -LODICUUES 



Fig. 120. Spikelet and Flower of the Oat. 

 (In the right-hand figure the flowering glume has been removed.) 



ing merely the barren end of the axis of the ear. Each 

 flowering- glume bears on its outer side, just below the tip, a 

 long bristle called the awn, which is sharply bent at its 

 middle. The flower itself resembles that of Wheat, con- 

 sisting of two lodicules, three stamens, and an ovary with 

 two feathery stigmas (Fig. 120). 



Oat differs from Wheat in having a short toothed ligule to 

 the leaf; a smoother and less hairy leaf - sheath ; in having 



