EXERCISE 25 

 A STUDY OF THE WHEAT HEAD 



Object. To examine the head of wheat and become 

 familiar with the shape and arrangement of its different 

 parts. 



Explanation. The head of wheat is commonly called a 

 spike. It is made up of several parts, of which the grain is 

 the most important. The head is composed of a single rachis 

 and several spikelets. The spikelets are attached to the 

 rachis. A fully developed spikelet has two or more kernels, 

 usually only two. There is an outer glume, flowering glume, 

 and a palea for each kernel, except when a third kernel de- 

 velops. The third kernel of a spikelet does not have an outer 

 glume. There is an undeveloped flower for each spikelet. 

 Sometimes the spikelets near the base of the head fail to 

 develop. The two divisions of a spikelet are similar in ar- 

 rangement of parts. There is an outer glume on each side 

 of the spikelet, and they partly inclose the flowering glumes. 

 The uppermost part of the outer glume is called the beak. 

 The notch just below the beak forms the shoulder, and the 

 heavy line running from the beak to the base is called the 

 keel. The flowering glume is just within the outer glume and 

 bears the beard or awn. The kernel is inclosed by the flower- 

 ing glume on the outside and by another husk called the palea 



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