DEPARTMENT OF EXPERIMENTAL EVOLUTION. 137 



three cruciate species, (Enothera cleistantha, atrovirens, and venosa 

 have now been grown. In many combinations the evidences of segre- 

 gation are clear, but in almost no instance does this segregation result 

 in apparently typical Mendelian groupings. 



A complete series of reciprocal crosses between each of the above- 

 mentioned species and a local hiennis-like species (unnamed) has given 

 results which parallel in an interesting manner the results secured 

 in the Fi families already reported. These studies have now been 

 extended to include two new cruciate species, (Enothera rohinsonii 

 and stenomeres, and two broad-petaled species, (Enothera oakesiana 

 and (Enothera biennis L. 



Special attention has been given to putative Mendelian characters, 

 such as nanism, brevistyly, pigmentation of rubricalyx, etc., with the 

 hope of discovering to what extent these characteristics are actually 

 distributed in typical Mendehan fashion. The inverse correlation 

 between the red pigmentation of the buds and that of the stems has 

 been fully confirmed in the hybrids between a form of Oenothera 

 rubricalyx and rubrinervis and between the same form and Oenothera 

 lamarckiana. 



PITCHER-LEAFED ASH TREES. 



This season has again added a few specimens of pitcher-leafed ash 

 trees to those previously noted in the pedigree families. The ratios 

 in these two families now stand 1.18: 1 and 2.17: 1 as compared with 

 the expected ratios 1:1 and 3:1, the pitcher evidently depending 

 upon the presence of a single Mendelian gene. The precocity of devel- 

 opment of this character, together with the degree of development 

 attained, are largely influenced by environmental factors. Most of 

 the trees have been transplanted, 153 which had not shown pitchers 

 during the first three seasons of growth being sent to an otherwise 

 vacant space in the northeast corner of the Hill Field of the Station for 

 Experimental Evolution, and 137 of those with pitchers being sent 

 to 131 universities, colleges, botanical gardens, etc. Other institutions 

 are to receive trees this fall. 



The survey of the area on which pitcher-leafed ash trees occur in 

 nature has been completed, and this area has been found to be about 

 twice as large as had been supposed heretofore, but no trees of consider- 

 able size have been discovered outside of the previously known area. 

 The area occupied by pitcher-bearing trees is about 400 meters in 

 diameter. All the ash trees on this area, from 1 dm. in height to large 

 trees, have been carefully examined for pitchers, with the result that 

 357 have been found with pitchers and 5,806 with only normal leaflets. 

 Trees having a trunk-diameter of more than 15 cm. are limited to a very 

 small area, about 400 square meters in extent. 



