376 AMERICAN JOURNAL OF BOTANY 



tions which furnished the materials for our earlier discussion of dimerous 

 and trimerous seedlings. The dimerous and hemitrimerous seedlings were 

 derived from the same parent plants in lines 75, 93, and 98. In lines 29, 

 139, and 143 the germinations were made from mass seed instead of from 

 the seed of individual parent plants. All of the seed, however, was grown 

 in the same experimental field in 1917. 



Since it has been shown in an earlier paper 2 that there is practically no 

 correlation between the anatomical characters of the trimerous and dimero^i 

 seedlings from the same parent plant, we are fully justified in using random 

 samples of hemitrimerous, trimerous, and dimerous seedlings for a com 

 parison of their vascular characters. 



A detailed account of the vascular topography of the dimerous and 

 trimerous seedling is presented in a previous paper by the writers, but may 

 be summarized very briefly here. Each primary polar bundle of the root 

 bifurcates in the base of the hypocotyl to form a &quot;primary double bundle,&quot; 

 which gives rise to two distinct and well separated strands in the central 

 region of the hypocotyl. In addition to these, there are usually present 

 in the hypocotyl a number of &quot;intercalary&quot; bundles, arising either de n&amp;lt;m 

 or by splitting of some of the primary strands. At the cotyledonary node 

 a rather complex vascular anastomosis takes place, from which the coty 

 ledonary strands depart and out of which the vascular system of the epicotyl 

 is organized. 



PRESENTATION AND ANALYSIS OF STATISTICAL DATA 



Base of Hypocotyl 



The frequency distribution of the various types of vascular organization 

 at the base of the hypocotyl is shown for all the available data in table I. 

 In this table the number of primary double bundles appears in parentheses, 

 while the number of intercalary bundles follows the + sign. 



Because of the relatively small numbers of hemitrimerous seedlings 

 which can be obtained and because of the irregularity of the frequency 

 distributions for bundle number, it has not seemed desirable in this paper 

 to consider the frequency distributions of the numbers of bundles of the 

 several types. Neither has it seemed desirable, on the basis of the rela 

 tively small series of hemitrimerous seedlings which can be obtained, tc 

 consider the relative variabilities of bundle number in the different regions 

 of the three types of seedlings as we did in our discussion of variation in th( 

 dimerous and trimerous types. We have, therefore, limited ourselves to 

 comparison of mean bundle number, leaving the question of variability 

 until larger series of countings can be obtained. 



2 Harris, J. Arthur, Sinnott, E. W., Pennypacker, J. Y., and Durham, G. B. Corrcla 

 tions between anatomical characters in the seedling of Phaseolus vulyaris. Amer. Jour. Bot 

 8: 339-365. 1921. 





