WHEAT 23 



and when germination takes place it expands and bursts the coats 

 of the grain, the roots about the same time breaking through 

 the enclosing coleorhiza. When a wheat grain is sown in the 

 ground it remains there, but the plumule grows upwards, and 

 appears above the soil as a single pale tube-like leaf; from a slit in 

 the tip of the latter the first flat green blade soon appears (/, Fig. 

 8), and is followed by a succession of single green leaves, the 

 younger ones growing from within the older ones in regular 

 prder. 



Ex. 13.— Soak some white wheat grains in water until well swollen out, 

 and note the following points : — The furrow along (the back of the grain, the 

 bearded tip, and the sid^ dpptisite the furrow. Keep them damp a. day. 

 The embryo, which is easily se'in through tHe semi-transparent coat, can be 

 removed by slitting round the circular cotyledon with a iieedle. Exatiiihe;i|s 

 structure, and compare with Fig. 6. 1 



With a sharp knife or razor cut through from back to front, so 'as to 

 divide the grain into two longitudinal halves, and note the floury endosperm 

 and the shape and parts of the divided embryo. 



Place a folded sheet of damp blotting paper on a plate, sow some soaked 

 wheat grains on it, and cover with a tumbler. The grains will germinate. 

 Watch their development up to the time the first green leaf appears, taking 

 out the embryo and examining it at different stages of its growth. 



There is difference of opinion as to which part of the embryo 

 is to be considered the cotyledon. Some authorities regard the 

 scutellum as the cotyledon, while others give this name to the 

 first sheathing leaf which comes above ground, and which has 

 no green blade (/, Fig. 8). Others, again, consider that the first 

 sheathing leaf is an extension of the scutellum, and the two 

 combined is therefore the cotyledon. In any case, there is 

 only one cotyledon present, and wheat therefore belongs to the 

 class of monocotyledonous plants. 



14. During the growth of the embryo of a wheat grain, it will 

 be noticed that the endosperm becomes soft and decreases in 

 quantity as the roots and plumule expand and develop ; the 

 endosperm is the food upon which the young plant depends 

 during the early stages of its life, the scutellum acting as a 



