168 



germination of the seed and the development of the plantlet to the 

 stage at which measurements were made. 



Since the development of the primordial leaves during the germina 

 tion and establishment of the seedling is relatively great, it seemed 

 quite legitimate to use the weight of green tissue produced by these 

 leaves as a measure of the physiological capacity of seedlings of various 

 types. The fact that these leaves are differentiated in the seed, does, 

 however, constitute a valid objection against their use as a measure 

 of the physiological capacity of the seedling. For such purposes a 

 constant based upon some organ developed later in the life of the 

 individual is desirable. 



One of the purposes of this paper is to present the results of deter 

 minations upon a later developed organ. The one chosen is the 

 first trifoliate leaf. 



This leaf was used because groups of plants of a higher degree of 

 uniformity can be selected at the time of maturity of this leaf thai? 

 at any later stage in the development of the plant, and because the 

 first compound leaf reaches a degree of maturity sufficient for the 

 purposes of the present study before the primordial leaves are too 

 old to be used for a series of determinations. It is, therefore, possible 

 to repeat, at a slightly later stage of development of the plant, the 

 determinations made on the primordial leaves in the first study as a 

 basis of comparison with the work already done and with the series 

 of constants to be obtained for the first compound leaves of the same 

 plants. 



In the first investigation the green weight of the leaf tissue served 

 .as the fundamental measurement. In addition to this character 

 certain measurements on the sap properties were also made. In the 

 study of the saps some difficulties were encountered, and it seemed 

 most desirable to discontinue that phase of the study temporarily 

 and to carry out determination of dry weight and water content 

 instead. These new measurements have, therefore, been added to 

 these for green weight. 



MATERIALS AND METHODS 



The materials upon which this study is based are the same as 

 those previously employed a mixture of slightly different strains 

 of navy beans. The seeds which were germinated in the fall and 

 winter months of 1916 were grown in field cultures in 1915. 



Seeds from individual plants were germinated in sand. In sorting, 

 the morphologically aberrant seedlings were laid aside with a normal 

 plant to serve as a check for each abnormal. An abnormal and a 

 control seedling from the same seed plant and germinated in the same 



