SUDAN GRASS AND RELATED PLANTS. 5 
shown in figure 4. Attempts to cross these two species artificially in 
the greenhouse have been successful in only a very small percentage 
of the trials, most of the attempts resulting in failure even under fa- 
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Fic. 3.—The natural distribution of Johnson grass and the grass‘sorghums. 
vorable conditions. There is apparently an antagonism or unfavor- 
able reaction between the reproductive organs of these two plants, 
which is rather decided evidence of their specific differences. 
