826 EXPERIMENT STATION EECORD. [Vol. 36 



found. Their occurrence on the upper side of the trees is explained by the fact 

 that rain in a wood nearly always falls vertically, with tlie result that the 

 upper side of the tree trunk, being more exposed, obtains a greater share of the 

 rainfall than the lower. The bryophytic vegetation is said to be most abundant 

 upon trunks with an inclination of more than 10°, while on perpendicular 

 trunks such vegetation is very nearly or entirely lacking. 



With trees standing in the open, a more upright habit of growth results, and 

 the occurrence of bryophytes on trunks is as a rule infrequent, but where they 

 are found, they may occur on all parts of the stem. This is claimed to be due 

 to the fact that in open ground the rain may come from all quarters. On such 

 isolated or exposed trees, lichens are of more frequent occurrence than mosses. 



A note on the inheritance of eye pattern in beans and its relation to type 

 of vine, F. M. Surface (Amer. Nat., 50 {1916), No. 598, pp. 577-586, figs. 3).— 

 The author has made a genetic study of the two types of beans previously 

 mentioned (E. S. R., 33, p. 635), carrying a few to the F2 generation. 



In addition to the two parent types, a third appeared in both the Fi and F2 

 generation, showing a piebald pattern as regards color distribution. This is 

 thought to be the expression of the heterozygous condition of the factorial 

 differences between the parent types. A provisional hypothesis for the types 

 thus far known is outlined on the basis of the admittedly scanty data which 

 have been obtained. Apparently the a;ene for the bush type of vine is closely 

 associated with that for one of the original patterns. 



A quantitative study of the factors influencing the weight of the bean 

 seed. — II, Correlation between number of pods per plant and seed weight, 

 J. A. Haekis {Bui. Torrey Bot. Club, JfS {1916), No. 9, pp. 485-49-^, figs. 4).— 

 This study, made in pursuance of those previously noted (E. S. R., 32, p. 521), 

 showed that throughout the 27 series of cultures used, representing five 

 varieties, the correlations for seed weight and number of pods per plant were 

 positive, but of small magnitude and variable. In both average magnitude 

 and variability the correlations for seed weight and number of pods per plant 

 agreed very well with those for ovule per pod and pods per plant and with 

 those for seeds per pod and pods per plant. 



The average value of the correlation for pods and weight was lower than 

 that for pods per plant and ovules per pod, and higher than that for pods per 

 plant and seeds per pod, but both of these differences are low and may not 

 be significant in comparison with their probable errors. 



On selective partial sterility as an explanation of the behavior of the 

 double-throwing stock and the petunia, Edith R. Saunders {Amer. Nat., 50 

 {1916), No. 596, pp. 486-^98). — This is a critical discussion of portions of the 

 preliminary paper by Frost, previously noted (B. S. R., 34, p. 237). 



Application of the pure-line concept to bacteria, L. J. Cole and W. H. 

 Wright {Jour. Infect. Diseases, 19 {1916), No. 2, pp. 209-221). — From a con- 

 sideration of experiences and observations in connection with the production 

 and study of bacterial cultures, the authors have concluded that much of the 

 variation observed in ordinary cultures is due to the selection, by investigator 

 or environment, of pre-existeut biotypes, and the suppression or extinction of 

 others. This leads to a temporary or permanent change in the character of the 

 type, and, in the latter case, gives rise to a change which may be erroneously 

 taken for a true hereditary mutation. Incomplete selection may be followed by 

 the reappearance of a suppressed type on the restoration of former conditions. 



The descendants of a single cell constitute a pure line, or clone, which can not 

 be modified by selection, though mutation is not excluded and does occur In 

 pure lines, both spontaneously and in response to environmental stimulus. The 



