Winifred E. Brenciiley 



153 



above tliat limit the plants are unable to make full use of their supply. 

 This, then, may be regarded as an argument for giving crops a fair 

 amount of room in order that they may obtain sufficient food, though 

 too thin planting may be wasteful as the plants may be unable to make 

 the best use of the available food. 



grams 



Fig. 4. Average dry weights of ten barley plants grown in water 

 cultures in nutrient solutions of different concentrations. 

 Dotted lines show limits of probable error. 



F. Solutions changed every four days. 



0. Solutions changed once during experiment. 



N. Solutions never changed. 



B. Light as a factor in competition. 



Although it is always stated that overcrowding of plants leads to 

 great competition for food and light, still little or nothing is definitely 

 known as to the extent to which competition for light affects the growth 

 of plants. As overcrowding increases, both factors come more and more 

 into play, and under ordinary cultural and experimental conditions it is 

 impossible to separate the two and to attribute any proportional action 

 to one or the other. The first experiments described above (pp. 144-151) 



Ann. Biol, vi « 11 



