EXPERIMENTS ON CUTTING OFF PARTS OF 



THE COTYLEDONS OF PEA AND 



NASTURTIUM SEEDS. 



AI'.F.CAII, C. IUMON. 



THE experiments to be described were undertaken as bear- 

 ing upon the general problem of the relation of food supply 

 to growth. They were carried on under the guidance of 

 Professor T. H. Morgan, to whom I am much indebted for 

 aid and suggestions. The variations in food supply were 

 produced in the pea and nasturtium, both dicotyledonous 

 plants, by cutting off part of the cotyledons, thereby reducing 

 the amount of food stored up by the parent plant for the use 

 of the seedling. The questions that arise relate to the effect 

 upon the size of the seedling, upon the differentiation of its 

 organs, and upon the number and size of the component cells, 

 caused by thus reducing the food supply. These questions may 

 be answered from the results of the experiments. 



As already stated, the pea and the nasturtium were the 

 plants selected. Before deciding on them, however, the 

 morning-glory, sweet-pea, radish, common bean, buckwheat, 

 mustard, cucumber, and pumpkin were tested as to their 

 suitability, by planting specimens of each with portions of 

 their cotyledons cut off. It was found that the peas and 

 nasturtiums, possessing large cotyledons, were more easily 

 manipulated, and that their seedlings were hardier than those 

 of the other plants. Their seedlings, moreover, grew rapidly, 

 so that differences in the relative size of the plants were early 

 noticeable and were well marked. Under favorable conditions, 

 however, good results might be obtained from some of the other 

 species, and it would be interesting to see to what extent they 

 corroborate those from the two plants here discussed. 



The seeds tested for availability, and subsequently all the 

 pea and nasturtium seeds, were treated as follows : After they 



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