14 INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATIONS. 



individual needs, for seed from the fasciated wild O. biennis of 1905, in which 

 the tendency toward fasciation was so marked, when sown in the garden in 

 1906 produced only one fasciation. The plants of this group flowered very 

 early, however, and the time of sowing: may have been as important a 

 factor as the change of environment, or even more so. 



That fasciation can be produced by mechanical injury has been known 

 for many years, and Sachs (6) and Goebel (16) both treat of the old exper- 

 iment where, by cutting- off the cpicotyl of certain germinating seedlings, 

 the side-branches forced out are flattened. Phaseolus miiltiflorus is most 

 commonly used, while de Vrics employed Agrostemna githago (19). Nas- 

 turtiums also respond readily, and as high as 60 per cent of fasciated 

 individuals was obtained in one water-culture. The injury must occur 

 just after germination, and this has led to the theory that the anomaly 

 is caused by overplus of nutrition rushing to undeveloped centers of growth 

 (16). The effects in the seedling are not lasting, for the flattened branches 

 soon revert to the normal shape. It is possible that the remoteness of the 

 stimulus from the meristems affected may have to do with this. In the 

 O2notheras the injury is to the initial meristem itself, and is of a nature so 

 delicate that no relatively coarse instrument can duplicate it artificially. 

 Repeated attempts were made to induce fasciation in the primroses with 

 incisions by fine sterilized needles, but the needles either destroyed the 

 apex altogether, in which case the side-branch did not fasciate, or failed to 

 reach it at all. Any incisions that could be made were so destructive com- 

 pared with those of the sort represented in plate v, fig. 13, that the attempt 

 was finally abandoned altogether. It is interesting to note, in support of 

 the theory of the influence of nutrition, that the effects in the (tnotheras 

 come during the rosette stage and just before flowering', the times when the 

 elaborated food supply is most abundantly centered at the growing apex. 



The discussion of the nature of fasciation has centered about the mor- 

 phology of the enlarged axis, whether it is the enlargement of a single- 

 growing point, as exemplified by Mouquin-Tandon (2), or whether it is the 

 adnation of several axes, as explained by Masters (3). After a careful 

 histological examination of faseiated growing tips of certain Phanerogams 

 and Cryptogams, Nestler (7) found no evidence in favor of congenital adhe- 

 sion. The growing line gave no sign of complexes of growing points, but 

 represented an enlarged area of meristematic cells. In the oenotheras there 

 has never been any evidence in favor of the concrescence theory. In one 

 single bifurcation for a short distance the epidermis closed around two 

 separate axes, but this was accidental grafting of two separate tips. The 

 phenomena of fasciation are phenomena of multiplication, of increase in 

 numbers of stems and leaves, and of the number of cells which enter into 

 their composition. Once the physiological balance of the growing cells is 

 changed and the chemical equilibrium altered by the peculiar stimulus of 

 the mechanical contact, the tendency to multiply develops, and frequently 



