i9i 7] CURRENT LITERATURE 417 



the float. Since the whole surface of the sieve tubes in this portion of the plant 

 is thus exposed to the gas contained in this float, it would seem possible that 

 considerable oxidation of foods is carried on in this internal atmosphere. The 

 gas in this float is shown to contain a little larger percentage of oxygen than 

 air. It may possibly be worth while to consider the presence of carbon mon- 

 oxide in plants in connection with the wide distribution of oxidases in plant 

 tissue and the possible mechanism of their reaction. 6 Langdox's thorough 

 demonstration of the presence of carbon monoxide in this cavity is a very 

 important piece of work, and great interest attaches to the possible relation of 

 this gas to the metabolism of the plant.— G. B. Rigg. 



Quantitative characters in beans. — By means of a statistical study of pole 

 and bush beans, Emerson 7 has analyzed the characters causing height varia- 

 tion in Phaseolus vulgaris. They are 3 in number and apparently segregate 

 independently after crossing. First is the manner of growth, which is either 

 "determinate" (bush type) or " indeterminate " (pole type), with the inde- 

 terminate habit completely dominant in the Fi generation, and showing the 

 typical 3 : 1 splitting in the F 2 generation. Such behavior he interprets as the 

 result of a single pair of freely segregating factors behaving in a Mendelian 

 fashion. 



Tschermak, using the hybrids Phaseolus vulgar isX P. multiflorus and the 

 reciprocal, found anomalous splitting in the F 2 , since some of the " short" 

 segregates produced "tails" in succeeding generations. He makes no mention 

 of habit of growth, and merely classifies the progenies as " tails" and "shorts." 

 The results of Tschermak need not be compared with Emerson's, however, 

 because in the former case the hybrids are interspecific, and in the latter inter- 

 varietal (intraspecific). 



The second character operative in determining height is number of inter- 

 nodes. The presence of this character was deduced from the fact that differ- 

 ent varieties of both pole and bush beans differed in the number of internodes 

 produced when grown under the same conditions. The question then arose 

 as to whether this tendency to produce few or many internodes could be 

 inherited independently of habit of growth. Suitable crosses were made and 

 the results seemed to answer the question in the affirmative, although the evi- 

 dence is admittedly incomplete. The factors determining this difference could 

 not be shown to be perfectly dominant, but apparent segregation followed 

 hybridization. This segregation was attended in the F 2 generation by a range 

 of variability exceeding that of the 2 parents. Emerson interprets this result 

 as due to the action of multiple segregating factors. 



third character involved in height is length of internode. The modi- 

 fication of this character by habit of growth made its behavior difficult to study. 



The 



6 Reed, G. B., Bot. Gaz. 62:53-64. 1916. 



Emerson 



Re- 



search Bull. no. 7. Xebr. Agric. Exp. Sta. pp. 73. 1916. 



