418 BOTAMCAL GAZETTE [may 



In order to have a standard of comparison between pole and bush bean types, 

 the first 5 internodes were measured and the means computed. For comparison 

 between different varieties of pole beans the mean of the first 5 internodes was 



1 



used. It was thought that the actual internode length found for some of the 

 bush varieties might not be representative of the potential length which 

 would have been attained by the upper internodes had not the production of 

 a terminal inflorescence hindered further growth. To test this supposition 

 crosses were made between a bush bean with long internodes and a pole 

 bean with short internodes. The resulting hybrid showed an intermediate 

 development in the F 1 and a wide range of variation in the F 2 generation. 

 Bush beans with shorter internodes and pole beans with longer internodes 

 than the parent types exhibited were obtained. Here again the variations 

 were attributed to the action of multiple, non-dominant, independently 

 segregating factors. 



In conclusion, the author points out that the results of other investigators 

 tend to show that quantitative characters in plants are inherited in two ways: 

 (a) they are due to the action of a single Mendelian pair of factors showing 

 complete dominance in the F r and a 3 : 1 ratio in the F 2 generation ; (b) they 

 exhibit an intermediate development in the Fj and a wide range of variation 

 in the F 2 generation. In class (a) belongs the determinate as opposed to the 

 indeterminate habit of growth. Characters such as length and number of 

 internodes fall into class (6). Such characters as those of class (b) have been 

 interpreted in 2 ways. Emerson, Tschermak, East, and others attribute 

 them to the interaction of many independently segregating factors, a theory in 

 accord with the multiple factor hypothesis of Nilsson-Ehle. Castle, 

 however, has interpreted such behavior as due, in some cases, to the modifi- 

 cation of a unit factor through hybridization. In the case of the bean crosses, 

 Emerson implies that the factor involved would be that which determines 

 habit of growth. After discussing this latter hypothesis and the assumptions 

 its adoption would necessitate, he rejects it in favor of the multiple factor 

 hypothesis. 



Since, therefore, the characters involved in producing an effect seem to 

 behave in different manners in inheritance, the author explains the variation 

 in height following hybridization between pole and bush beans as due to the 

 modification of the expression of a unit factor by the presence or absence of 

 a number of factors producing other effects (as, for example, the effect of the 

 determinate habit of growth on the potential length of internodes and on the 

 number of internodes, etc.). However, the author disavows any intention of 

 maintaining that this is the only possible explanation, and suggests that it may 

 have to be modified to suit the results of further selection and hybridization 

 experiments. — Wilbur Brothertox. 



Philippine forests. — Our knowledge of the economic importance and the 

 environmental conditions of some tropical forests has been advanced by a 





