lo March, 1912.] 



W'Jieat and its Cultivation. 



starch, is insoluble in water, is acted on by a ferment present in the grain, 

 and is broken down into diffusible proteids called peptones. 'J'hese soluble 

 peptones, as well as other nitrogenous compounds of lesser importance 

 (amides and amido-acids) diffuse from cell to cell and nourish the growing 

 tissues of the young embryo. It is not long before the reserves of food 

 in the .seed are exhausted, and henceforth the young plant must lead an 

 independent existence. At this stage an examination of the root system 

 will reveal several interesting feature.s. 



Along the greater portions of the roots, minute delicate fibrils will be 

 observed. These are the tender root hairs which push their way through 

 the minute interstices between the soil particles and apply themselves 



ro. TRANSVERSE SECTION OF WHEAT ROOT (x 270). 



closely to the uneven edges of the soil grains. Microscopical examination 

 proves them to be long tubular appendages — mere delicate prolongations of 

 the epidermis. The epidermis forms the external Jayer of the root. and. 

 as may be seen in Fig. lo, it is composed of cells clo.sely packed together 

 with no interstitial spaces or openings of any kind. In this respect, 

 as will be shown later, it differs markedly from the epidermis of the leaf. 

 From this absence of openings it will be clearly apparent that the plant, 

 so far as the root system is concerned, is quite incapable of appropriating 

 food of a .solid character from the soil. Whatever nutrients are obtained 

 from the soil, therefore, must be liquid or gaseous in character. Now the 

 particles that compose a normal soil in good condition are very irregular 



