I9 2i] HARRIS PHASEOLUS 153 



extent a highly abnormal race differs from the parental strain 

 from which it originated. 



Materials and methods 



In this paper the characteristics of a fully heritable teratological 

 race are considered. The material was furnished by a tetracotyle- 

 donous race, the origin and general characteristics of which have 

 been considered elsewhere. 4 The tissue of plants of the tetra- 

 cotyledonous race were compared with those of the normal line 

 from which it originated. 



Seeds of the two series grown in the same field in 1917 were 

 germinated in flats of sand in 1919. Four lots of fifty seeds each, 

 two of the tetracotyledonous plants and two of the normal ances 

 tral line, were germinated in alternate positions in the same flat. 

 Conditions, therefore, were as nearly comparable as possible in the 

 germination of the two series. When the seedlings were of the 

 proper size for potting, one seedling of the tetracotyledonous race 

 and one normal control taken from the same flat were transferred 

 to 3-inch pots of soil, where they stood until they were ready for the 

 collection of samples of tissues. Weighings were then made of the 

 primordial leaves in the two cases. Thus, although weight and 

 other characteristics vary from sample to sample because of age 

 and the innumerable slight influences of significance in growth, 

 the aberrant plants and their controls from the very beginning had 

 ; as nearly as possible identical environment. However much the 

 pairs combined in the same sample may differ among themselves, 

 there seems no possibility of considering that the differentiation 

 here shown to exist between the morphologically typical and the 

 morphologically aberrant individuals is due to any extrinsic cause. 

 In the absence of any knowledge of the amount of variation in the 

 characteristics of the leaves to be investigated, it was impossible 

 to compute in advance the size of the sample which should be taken. 

 Accordingly it was arbitrarily fixed as 100 plants. 5 



4 HARRIS, J. ARTHUR, A tetracotyledonous race of Phaseolns vulgaris. Mem. 

 N.Y. Bot. Gard. 6:229-244. 1916. 



, De Vriesian mutation in the garden bean Phaseolus vulgaris. Nat. 

 Acad. Sci. 2:317-318. 1916. 



5 Sample 305 contained 96 plants, sample 252 only 81 plants, and sample 259 

 contained 138 plants. 



