110 HARRIS AND AVERY: MORPHOLOGICAL VARIATIONS 
node in the case of plants showing various structural abnormalities 
at the first two nodes. 
Phaseolus is well suited for such investigations. The normal 
seedling has two cotyledons, inserted at the same level, and two 
opposite primordial leaves. A large number of structural varia- 
tions, four types of which will be considered in this paper, may 
occur. The chief disadvantage lies in the rarity of many of the 
variations in the lines with which we have dealt. The securing of 
adequate series is excessively laborious. The present paper is 
based upon a careful study of the variations in the first three nodes 
of 16,348 plants, which were selected from about 450,000 seedlings 
examined for the characters of the first and second node. 
When in the following paragraphs we refer to normal and 
abnormal plants or seedlings, it must be understood that this 
applies to the characteristics of the individual as determined ‘on 
the basis of the first two nodes, the cotyledonary and the pri- 
mordial only. In its later development the “abnormal” plant 
may remain ‘“‘abnormal’’ or become “normal,’’ and the ‘‘normal’’ 
plant may either continue to be “normal” or become “abnormal.” 
The nature and method of Classification of the abnormalities 
dealt with will be discussed in the presentation of the data below. 
MATERIALS AND METHODS 
The materials upon which this study is based are a series of 
lines of White Navy beans grown at the Station for Experimental 
Evolution during the past several years. The seeds were har- 
vested from field cultures in 1915 and germinated in sand in the 
autumn of 1916. 
Seedlings which were abnormal in the characters of the first 
or second node, i. e., in the number or insertion of the cotyledons 
or of the primordial leaves, were sorted out for potting in soil and 
subsequent study of the third node, that normally giving rise to 
the first compound leaf. 
For each abnormal individual, a normal control seedling from 
the same parent plant was taken at random to serve as a basis of 
comparison. Both were potted in soil and grown to a stage when 
the characteristics of the third node could be accurately deter- 
mined. 
