176 CHEMICAL COMPOSITION OF PLANTS 



lack of this compound. ' Lodging ' is, however, due to a weakness 

 caused chiefly by want of proper amount of light for normal 

 growth, and firm-strawed, well-developed plants of maize, oats, 

 and other cereals have been grown in v\ater-cultures without 

 silicon. Moreover, analysis has shown that the straw of 'lodged' 

 crops generally contains more silicon and is much more brittle 

 than straws of crops which have stood upright. 



Jodin grew four generations of maize plants without any silicon. 



Cultures of oats from which this element is missing do not 

 yield so much grain as those to which it is applied. 



Silicon is absorbed from the soil in the form of soluble silicates, 

 the bases with which the latter are associated being apparently 

 utilised in the nutritive processes. 



Sodium in the form of sodium chloride is common in all plants, 

 but is absorbed in greatest amount by halophytic plants which 

 flourish on salt-marshes near the seashore, or inland near salt- 

 mines and salt-lakes, where the amount of salt present in the soil 

 is more than can be tolerated by ordinary inland plants. 



Many halophytes, such as Glasswort {Salicorfiia herbacea L.), 

 Saltwort (6'a/.f«?/fl Kali L.), beet and mangel,and %^(i<:\es,Qi Atriplex, 

 belong to the Chenopodiacese (p. 349.) Several cultivated cruci- 

 ferous plants, such as the cabbages and seakale, are descendants 

 of halophyte ; asparagus is another example of the same class. 



Culture experiments have shown that even the most typical of 

 these halophytes can be grown without salt ; nevertheless when sup- 

 plied with it, they present a different appearance and have different 

 physiological characters from plants deprived of the compound. 



Under the influence of an abundance of salt the vegetative 

 organs become plumper, more fleshy and succulent and transpire 

 less than they do when grown without much salt. 



Plants, such as the cereals and others not habitually growing 

 near the sea, are killed by solutions containing more than i or i J 

 per cent., whereas sea-beet and certain species of Atriplex are 

 not destroyed by solutions containing 3 or 4 per cent, of salt. 



