Studies of Teratological Phenomena. 77 



the constant normal and constant fasciated races continue to remain 

 inconstant, even though thej^ may all be grown from seed of a single 

 self-fertilized plant. Such races are usually plants which are naturally cross- 

 fertilized and hence may be heterozygous in many internal factors. The 

 segregation of these factors, even in the gerra-cells of a single selfed plant, 

 may produce a very diverse progeny. As the development of one factor 

 may be hindered or helped by the presence or the absence of others, one 

 may conclude that part of this eversporting condition is due to the 

 segregation that takes place in each generation. Further, more than 

 one primary factor may be involved in producing fasciation in some 

 races of plants. In attempting to explain the eversporting character 

 of de Vries' fasciated races, one must not forget the prevalence of the 

 various external factors, which especially in an old settled country, are 

 always on hand to commit depredations. When these external factors 

 operate in the form of an insect, they are very hard to trace, as has 

 been shown by Knox and others. M}' own experience with Oenotheras 

 has shown me how hard it is to guard against such factors. I grew 

 200 seedlings from two very fasciated wild plants of Oenothera hiennis, 

 which were obtained for me through the kindness of S. M. Blake of 

 the Gray Herbarium. They were grown under conditions generally held 

 to be favorable to the development of fasciation, and on ground only a 

 few rods from which in former years, many fasciated Oenotheras had 

 been observed. Of the 200 seedlings only one was fasciated and that 

 only to the extent of a small twig. It is obvious that in this case, 

 fasciation was not hereditary in the sense in which we ordinarily use 

 the term, yet had I previously believed such characters to be inherited in 

 this inconstant manner, I would have never considered the true cause 

 — insect mutilation. 



Summary of Parts B and C. 



1. The character fasciation is widely distributed in the plant world, 

 both in wild and cultivated plants. Sufficient data have not been 

 collected to prove that it is absent from any taxonomic group. 



2. Certain ecological conditions are favorable to its development, 

 but these conditions are not necessarily essential. 



3. The character fasciation may occur in almost any part of the 

 plant. Morphologically, it appears to be an enlargement of a single 

 growing point, so that considering the fasciated plant as a whole, the 

 amount of tissue is greatly increased over that of its normal relatives. 



