STOUT: DUPLICATION AND COHESION 483 
instead of one, accompanied by their cohesion or incomplete separation. 
In both the factor of cohesion is present, but in the cotyledons it leads 
to reduction in the number normal to the species, while in the stem it 
tends to reduce the duplication to the single stem-element that is 
normal to the species. 
The occurrence of the sort of duplication described above has now 
been observed in four generations. Thirty-five plants of the 1913 
crop of the variety red-leaved Treviso were grown from commercial 
seed. In 14 plants the main axes were decidedly duplex, the length 
of the segments showing duplication ranging from a few inches to 
about three feet. The stems of the other 21 plants showed no sign 
of duplication. All plants of this generation which were tested were 
found self-sterile from physiological incompatibility, so it was not 
possible to obtain self-fertilized seed. Numerous crosses were at- 
tempted between plants, but only one cross attempted was compatible. 
In 1914, 12 plants were grown as progeny of the cross between two 
plants which were quite alike in exhibiting duplication of rather inter- 
mediate development. In all 12, duplication developed. The vari- 
ability in degree of duplication was marked and ranged from very 
slight indications to very decided cases of torsion and lesion. One 
plant developed too late in the season to be tested for self-fertility, 
but the other 11 were all self-sterile. However, some compatible 
crosses were made from which 43 plants were grown in I9QI5. 
Of the 1915 crop, 39 of the 43 plants exhibited duplication to some 
degree. In one plant the two elements were completely separate from 
the very base upward (no. 7). In several plants torsions and lesions 
were strongly developed. Four plants were apparently not in the 
least fasciated and in each of these the phyllotaxy was regular and 
single. 
In the 1916 crop, 150 plants were grown. Two of these were froma 
self-fertile plant (the only one of the 1915 crop that was found to be self- 
compatible in any degree). The 148 other plants of this generation 
were from six different crosses involving eight different parent plants, all - 
of which, however, exhibited duplication in some degree. This genera- 
tion was descended from three generations of parentage that exhibited 
duplication. There was duplication to some extent at least in 144 of 
these plants. Six appeared to have a single stem-element with regular 
phyllotaxy; these six plants were distributed among the offspring of 
three different crosses. 
One plant of the 1916 crop exhibited a noticeable fasciation of the 
ribbon type in the upper branches in addition to duplication and 
cohesion in the main axis. The tips of the main branch and of various 
laterals were broadly flattened and the branching was reduced so that 
