Journal of Agriculture, Victoria, [lo March, 191 2„ 



produced. It is probable that under Australian conditions the amountr 

 required would be even higher than this. Assuming, however, in the- 

 absence of definite figures for Australian conditions, the results obtained 

 by Hellriegel, and as'^nming that the ratio of grain to straw in an average^ 



wheat crop is 2 : 3. then 

 a 20-bushel wheat crop 

 would need to transpire- 

 an equivalent of 6 inches 

 of rain, and a 30-bushel 

 crop would need approxi- 

 mately 9 inches of water. 

 In other words 6 inches 

 of absolutel v effective 

 rain during the growing 

 period should be theore- 

 tically sufficient for the^ 

 requirements of a 20- 

 bushel crop of wheat pro- 

 \ided the soil was in good 

 condition at the time of 

 germination. Such re- 

 sults are not obtained in 

 practice, however, be- 

 cause under the most per- 

 fect methods of soil culti- 

 \'ation, losses of mois- 

 ture from the soil other 

 than by the transpiration 

 Obviously there should be a sort of equilibrium 



15. LONGITUDINAL SECTION OF A FEDERATION 

 WHEAT STEM THROUGH THE VASCULAR 

 BUNDLE SHOWING THE CONSTRUCTION 

 OF THE CONDUCTING VESSELS. 



current are inevitable. 



existing between the amount of water transpired and the amount absorbed 

 by the roots. Frequently the former is in excess of the latter and wilting 

 results. This often takes place in a wheat field in early spring when hot: 



16. CROSS SECTION OF A WHEAT LEAF SHOWING EPIDERMAL CELLS, 

 MESOPHYLL, AND VASCULAR BUNDLES. 



winds are prevalent or when wheat has been thickly sown or manuring 

 has been excessive. Under these circumstances transpiration from leaf and 

 stem is not infrequently in excess of the amount of water taken up by 

 the roots and injury results. The water is mainly transpired through 

 the stomata of the leaves and as the number of stomata is usually greater 



