GRAMINE.5i. CEREALS 489 



corn crops very frequently become 'laid' or 'lodged.' The 

 straw is weak and it is found that the second and third inter- 

 nodes near the ground are longer than usual and the cells 

 beneath the epidermis and round the vascular bundles, upon 

 which the stems depend for mechanical support, are longer and 

 have thinner walls than those of straw which is not laid. 



The weakness is not caused by a deficiency in the amount of 

 silica in the cell walls as was formerly imagined, but is due to 

 an inadequate supply of light to the young plants, the lower 

 parts being etiolated by overcrowding. 



Nitrogenous manures tend to the production of much leaf 

 surface in all plants, and when used in excess on corn crops the 

 plants shade each other and are liable to become laid in 

 consequence. 



Heavy rain and wind increase the evil, but the weakness may 

 be such that the weight of the upper part of the straw is sufficient 

 to make it fall without the aid of wind or rain. 



It might be imagined that well-tillered crops, where many 

 stems arise from each plant, would be specially subject to 

 'lodging.' This is, however, not usually the case ; the 'tillering' 

 process is dependent upon light, and the fact of its having gone 

 on extensively is evidence that each plant has had an adequate 

 exposure to light ; shaded plants ' tiller ' very little. 



Thick-sowing or drilling in too close rows promote 'lodging,' 

 for ;from the first — soon after germination — the plants shade 

 each other. 



Flowering and Fertilisation. — Most cereals open their 

 flowers in the morning from four to seven o'clock and only when 

 the temperature rises to about 75° F. At the time of flowering 

 the flowering glume and pale are forced apart by the increased 

 turgidity of the lodicules, and the anthers are pushed out by the 

 rapid growth of the filaments of the stamens. At the same time 

 much of the pollen is shed into the air, but in almost all cereals 

 some of it falls on the feathery stigmas of the same flower, and 



