32 THE WHEAT PLANT 



skin within which remains only a watery solution of the last dissolved 

 reserves ; the plant has become independent of the parental store and is 

 capable of manufacturing its own plastic materials. 



The same sequence of events as that described above is observed 

 in the germination of grain sown in autumn in the open field, but enzyme 

 action and growth are less rapid, owing to the lower temperature at this 

 season. Grains sown during the last few days of October (1914) had 

 their first green leaves completely unfolded in three or four weeks, and 

 at the end of November the endosperm had completely disappeared 

 from the majority of them. 



The vitality of the wheat grain and the possibility of its germination 

 capacity being retained for long periods has been the subject of much 

 controversy. 



Wheat grains of great antiquity have been unearthed from ancient 



FIG. 21. Section of a portion of the pericarp and aleuron layer of a grain 16 days from 

 beginning of germination, a, Cross layer of pericarp ; b, testa ; c, aleuron layer 

 (X275). 



stores and tombs in different parts of the world. In many cases they 

 are completely carbonised, and in this state are merely friable masses of 

 charcoal with the form of the grain : such are those obtained from the 

 neolithic pile-dwellings of Switzerland and the pre-Roman settlements 

 of this country. Specimens from vases deposited in the tombs of ancient 

 Egypt, where they have been kept dry, away from atmospheric changes, 

 show much less alteration, and, except that they are a dark reddish-brown 

 colour as if scorched, appear normal in size and shape. 



I examined a number found by Professor Flinders Petrie in the 

 Graeco-Roman cemetery at Hawara (about first century B.C.). These were 

 plump, and similar to some forms of T. durum grown at the present day. 

 The pericarp was a dark reddish-brown tint, its structure unchanged. 

 The aleuron layer had retained its original shape, with normal cell walls 

 and typical round aleuron grains within. 



The parenchyma of the endosperm contained unaltered starch grains 

 which stained a purple colour with iodine, but the delicate cell walls of 



