152 BOTANICAL GAZETTE [SEPTEMBER 



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 germination 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, however, constitutes 

 a valid objection against their use as a sole measure of the physio 

 logical capacity of the seedling. For such purposes a constant 

 based upon some organ developed later seemed desirable. 



In a second study, 3 therefore, the tissue weight determinations 

 were extended to the trifoliate leaves of the third node, as well as 

 to the primordial leaves of the second node. This leaf was used 

 because groups of plants of more uniform development can be 

 selected at the time of maturity of this leaf, than at any later 

 stage, and because the first compound leaf reaches a degree of 

 maturity sufficient for the purpose of the present study before the 

 primordial leaves are too old to be used. It is possible, therefore, 

 to check results by determinations made on organs differentiated 

 both in age and in structure. 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 diffi 

 culties were encountered, and it seemed desirable to discontinue 

 that phase of the work temporarily and to carry out determinations 

 of dry weight and water content instead. The present study, 

 therefore, has to do only with the green weight, the dry weight, and 

 the percentage of dry matter. 



Recent investigations fell into two phases. The first was an 

 endeavor to determine to what extent seedlings which are morpho 

 logically aberrant in the race to which they belong also differ from 

 the normal seedling of the race in their physiological characters, 

 in so far as these can be measured by the capacity for the production 

 of tissue. In the second the investigation was extended from intra- 

 racial to inter-racial comparisons, to ascertain if possible to what 



3 HARRIS, J. ARTHUR, Further studies on the interrelationship of morphologica- 

 and physiological characters in seedlings of Plta-seolus. Brooklyn Bot. Card. Mem 

 i :i67-i74. 1918. 



