eb., 1921] HARRIS AND OTHERS SEEDLINGS OF PHASEOLUS 65 



&amp;gt;airs of abnormal and normal seedlings were, in three of the lines investi- 

 ated, derived from the same parent plant. 



Furthermore, care was taken that seedlings compared were grown 

 inder essentially identical conditions, in order to reduce to a minimum the 

 nvironmental influences which might possibly tend to bring about dif- 

 rences between them. Seeds from individual plants were germinated 

 n flats and harvested as soon as possible after they broke through the sand. 

 Thus all seeds not only developed under the same parental environment but 

 vere germinated under sensibly identical conditions, were collected simul- 

 ;aneously, anjd were in consequence sectioned at essentially the same stage 

 )f maturity. 



Because of the rapidity with which seedlings change and the great 

 nfluence of temperature upon growth, it is difficult to standardize, or exactly 

 :o describe, the stage of development at which the seedlings were taken. 

 Most of them were placed in alcohol before or very soon after the primordial 

 eaves had unfolded. Thus a fairly uniform and early stage of development 

 was secured. 2 



Free-hand sections were cut and mounted temporarily. When neces 

 sary, phloroglucin and hydrochloric acid were used to bring out the vascular 

 bundles. The general vascular topography of the seedlings was studied, 

 but the data for the statistical analysis of the seedling anatomy were 

 derived from a careful count of the number of vascular bundles at various 

 levels in the seedling. Because of a certain amount of variation in the 

 number of bundles with position in the organ, counts were made in definite 

 regions only the basal region of the hypocotyl (just at the point of tran 

 sition from &quot;root structure&quot; to &quot;stem structure&quot;); the median region of 

 the hypocotyl; and the median region of the epicotyl. In three series 

 counts were also made of the protoxylem poles in the upper portion of the 

 primary root. 



The number of data available for the several regions differs because of a 

 change in the plan of the work. Sectioning and counting were begun by 

 two of us at Cold Spring Harbor in the summer of 1917 and continued with 

 the assistance of Miss Eunice Kinnear in the summer of 1918. This work 

 was confined to the mid-regions of the hypocotyl and epicotyl. From a 

 statistical study of these data it seemed desirable to have a further series 

 of countings made independently by a specialist in vascular anatomy. 

 The work was, therefore, continued at Storrs during 1918, 1919, and 1920. 

 We are greatly indebted to Miss Flora Miller for assistance in this phase of 

 the work. At Storrs, sections were made at the base of the hypocotyl as 

 well as in the mid-region of hypocotyl and epicotyl. In three series, sections 

 were made of the root as well. 



The bundles vary considerably in size, the largest being well developed 



2 Some of the seedlings of line 143 were allowed to become a little older, but there is no 

 evidence of change in bundle number with age: 



