2o8 Scientific Proceedings (115). 



for tissue production as measured both by green weight and dry- 

 weight in primordial and first compound leaves than do their 

 normal controls. 



In a subsequent series of investigations we have instituted 

 comparisons between the highly abnormal seedlings of a tetra- 

 cotyledonous race of Phaseolus 1 and the normal seedlings of the 

 parental race from which it originated. 



The tetracotyledonous race is characterized by a modal number 

 of four cotyledons and four primordial leaves but both of these 

 characters are highly variable. 



Classifying the tetracotyledonous plants according to number 

 of primordial leaves, we have the mean green weight and the mean 

 dry weight of primordial leaf tissue in teratological and normal 

 seedlings shown in the accompanying table. 



The data are given as average weights per plant and per leaf. 

 The average per cent, of dry substance is shown in the final column 

 of the table. All the values are averages of constants based on 

 samples of approximately 100 plants. 



The data show that without exception the mean green weight 

 and the mean dry weight per plant of primordial leaf tissue is 

 lower in the tetracotyledonous race than in the normal race. 



The mean percentage differences (obtained by using the con- 

 stants for the normal plants as a base) for green weight per plant 

 range from —3.10 for the plants with six primordial leaves 2 to 

 —31.55 per cent, for group of plants with 2 primordial leaves. 



The percentage differences for dry weight of primordial leaves 

 in tetracotyledonous and dicotyledonous races vary from —7.93 

 per cent, for the group of plants with 6 primordial leaves to —32.55 

 for plants of the tetracotyledonous race with 2 primordial leaves. 



It will be noted that the difference between the abnormal 

 and the normal plants decreases as the number of primordial 

 leaves on the abnormal plants increases. 



The results for the average green and dry weight per leaf in 

 the mutant and normal series fully substantiate the conclusions 



1 Harris, J. Arthur, Proceedings National Academy of Science, 1916, ii, 317-318. 

 Harris, J. Arthur, Memoir, N. Y. Botanical Garden, 1916, vi, 229-244. 



2 Theoretically plants with 7 leaves should have shown a smaller difference than 

 seedlings with six leaves but the number of seedlings available was not so large and 

 the constant is therefore not as trustworthy. 



