Visible Mutations 247 



Interesting visible mutations have also been produced in a 

 large number of plants, only a few of which can be mentioned 

 here. In Stadler's work on barley he observed a very large 

 number of seedling mutations. Although these mutations af- 

 fected many parts of the plant and influenced such fundamental 

 properties as the manner in which the stem grows, many of them 

 were chlorophyll characters, producing the same types of chloro- 

 phyll deficiencies that have occurred spontaneously. Similar 



Fig. 75. Lemon lethal, an X-ray induced mutation in Habrobracon. 

 (Courtesy of Dr. A. R. Whiting.) 



studies have been carried out by Gustafsson, who identified 

 about six hundred chlorophyll deficiencies, most of which he 

 could group into one of five types. These types are not clear- 

 cut but include albinos and plants which are yellow, greenish, 

 or striped. In addition to these defects in the chlorophyll ap- 

 paratus, Gustafsson has obtained a number of other changes 

 affecting the morphology or physiology of the plant. They in- 

 clude such characters as the erectoid types, which have more 

 compact, erect heads with shorter and stiffer straw, types which 

 flower considerably later than normal plants, plants with larger 

 kernels, and types with brownish or with yellow instead of 



o 



yellow-green kernels. Gustafsson and Aberg found a very in- 

 teresting X-ray mutation in Golden barley. In this cultivated 

 variety the glumes are linear and have short awns. In the mu- 

 tant type, the outer glumes are identical in size and shape with 



