Growth Hormones in ''Lazy" Maize 309 



gene. This is probably also an oxidation. In the wild-type fly, 

 further chemical changes occur which convert this c?i+ hormone 

 first into a tan pigment and then into the brown pigment. This 

 chain of reactions is not well understood and may be modified 

 by other mutant genes. In the scarlet {stst) and cardinal {cdcd) 

 types, the cn+ hormone is affected in such a way that the full 

 amount of brown pigment is not produced. 



Much of the early knowledge of these hormones resulted from 

 transplantation studies. If pieces of tissue (anlage) which will 

 develop into an eye are injected into the body cavity of another 

 larva, they will develop into normal eyes within the body cavity. 

 They can later be dissected out and studied to observe whether 

 the tissues of the host have produced any changes in them. 

 When wild-type eye tissue is transplanted into vermilion or 

 cinnabar hosts, the transplanted eyes develop into wild-type 

 eyes because they secrete their own v+ and cn+ hormones. If, 

 however, pieces of eye tissue from vermilion or cinnabar are 

 transplanted into wild-type larvae, they develop into wild-type 

 eyes. In their own bodies they would be vermilion or cinnabar 

 because of the absence of i^+ or cn+ hormone. In the wild-type 

 flies, however, large amounts of these hormones are produced 

 and they are diffusible. They then diffuse into the developing 

 transplanted eye tissue and supply the hormones necessary for 

 the development of these transplanted eyes into the wild type. 



An interesting feature of these hormones is that they are 

 apparently not specific to Drosophila. In the moth, Ephestia, 

 a hormone is produced which seems identical in every way with 

 v+ hormone. This hormone can also be synthesized by a certain 

 species of bacterium. This species of bacterium will produce a 

 large amount of a substance that is apparently identical with 

 i'+ hormone if it is grown under aerobic conditions on a medium 

 which contains tryptophane. In fact it was this situation which 

 led to the discovery of the relation of tryptophane and ky- 

 nurenin to the v^ hormone. 



Growth Hormones in "Lazy" Maize 



Another example of a known hormonal situation correlated 

 with gene action is the behavior of "lazy" maize. This type is 

 homozygous for gene la in the fourth chromosome. If normal 

 maize plants are tilted at an angle or are placed on their side 



