78 BOTANY 



not strictly accurate ; it is really the fruit and contains 

 the seed, but the testa of the seed and the wall of the fruit 

 are so closely united that we cannot separate them. The 

 grain of wheat is a small ovoid body with one side flattened 

 and grooved down its length. At the back, 

 quite at the lower end of the grain, is a little 

 . wrinkled area, which marks the position of the 

 embryo, above which and forming the greater 

 part of the grain is the endosperm, filled with 

 food for the young plant during its early growth 

 or germination. A section of the grain is shown 

 in Fig. 34. 



The grass embryo possesses a single large 

 cotyledon which is at first terminal and con- 

 tinuous in a straight line with the radicle, 

 while the plumule grows out laterally some 

 p lG little distance below the apex. As it grows 



Longitudi- the cotyledon becomes forced over to one side, 

 n ^ s?" ^ and the plumule and radicle come to lie in a 

 oat grai ^ straight line, as in the dicotyledons. The 

 cotyledon then develops along the side of the 

 rest of the embryo, separating it from the endosperm. 

 The side of it which is in contact with the latter is the 

 part which absorbs the food in the endosperm cells. In 

 other seeds the cotyledon remains in a line with the radicle, 

 the whole embryo being surrounded by the endosperm. 

 In germination, however, the upper end of the cotyledon 

 is the last to leave the seed coat, remaining there and 

 absorbing the endosperm as long as any persists. 



If we soak some grains of wheat or barley and keep 

 them warm germination soon begins. The radicle pro- 

 trudes as a little white body from the micropyle ; looking 

 along the back of the grain we can notice a little pointed 

 prominence gradually making its way in the other 

 direction under the skin and ultimately emerging at the 

 other end ; this is the plumule. As it gets larger it dis- 



