IV.] DEVELOPMENT OF WHEAT 6i 



other bulbous plants the sequence of getting and spend- 

 ing is not perhaps so clearly seen as in the autumn 

 crocus : in the common crocus, for example, the leaves 

 are almost contemporaneous with the flowers ; with the 

 tulip and daffodil it requires closer observation in 

 order to realise that the processes of manufacture and 

 storage are quite distinct from those of flower and seed 

 formation, because the two are going on almost at the 

 same time. Just in the same way, even with annual 

 plants like wheat, we may distinguish the processes and 

 periods of manufacture and storage, followed by the 

 later process of migration, when the accumulated 

 material is stored up afresh in the seed as a reserve 

 wherewith to give the young plant a start in life. The 

 course of existence of a wheat plant merits particular 

 examination from this point of view, and the changes 

 taking place may be studied in some detail because 

 they are typical of much of what is going on in all 

 plants. The starting-point is the seed sown in autumn ; 

 after it germinates the blades grow 2 or 3 inches high, 

 but there they generally remain for the rest of the 

 winter, often indeed appearing to dwindle because of 

 the way the leaves lie down with the first frost. But 

 though the growth above ground is almost at a standstill, 

 the material that is being formed by assimilation is used 

 up for the formation of roots, which are pushing deeper 

 into the soil all through the winter. It is at this stage 

 that the foundation is laid for the future crop, and a wet 

 autumn and winter, by limiting the aeration of the soil, 

 causes a restricted root development which is always 

 followed by a poor yield. For example, if we compare 

 the crops upon three of the manured plots at Rotham- 

 sted, we get the following results for the ten wettest 

 and the ten driest winters (November to January 

 inclusive) between 1852 and 1904: — 



