^ PREFACE. 



trj An important branch of Agricultural Research to-day is the study of the food requirements 



\ of the various crops. The effects of with-holding one or other of the indispensable food- 



^ constituents are characteristic for each crop, and can be demonstrated pictorially from 



^ both Held and pot-experiments. 



Until quite recently, the only method of demonstrating the results of such experiments, 



was by means of retouched and coloured photographs or by coloured drawings. Each of 



g> these methods was liable to inaccuracies and neither of them appeals to us at the present 



day. With the advance of colour photography and the colour printing processes, however, 



'^ we are to-day in a position to procure reproductions in natural colours, which ought to 



^ cast no doubt as to their accuracy for illustrating such experiments as we have under 



consideration in the following pages, 

 i The present work is an attempt to portray, by means of these new processes, the effects 



of starvation, due to with-holding the several necessary food-constituents, on various crops. 

 The experiments demonstrated were carried out by several of the leading Agricultural 

 Experiment Stations in Germany. 



The Agricultural World as a whole, and no less we ourselves, owe a great deal to those 

 eminent Scientists who have imparted to us in these pages, their knowledge concerning 

 some of the problems of plant-nourishment as shown by experiment. To Professor Kriiger, 

 Bernburg; Professor Remy, Bonn-Poppelsdorf; Professor Schneidewind, Halle a. S.; and 

 Geheimer Regierungs-Rat Professor von Seelhorst, Gottingen., we extend our heartiest thanks. 



S KALISYNDIKAT G. m. b. H. 



^ ' ~^ Agricultural Department. 



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