UNITED STATES DEPARTMENT OF AGRICULTURE 



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I BULLETIN No. 406 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



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Washington, D. C. 



PROFESSIONAL PAPER 



September 5, 1916 



DISTINGUISHING CHARACTERS OF THE SEEDS OF 

 SUDAN GRASS AND JOHNSON GRASS. 



By F. H. HiLLMAN, Assistant Botanist, Seed Laboratory. 



CONTENTS. 



Page. 



Introduction 1 



Distinguishing characters of the seeds of 

 Sudan grass 3 



Page. 

 Distinguishing characters of the seeds of 



Johnson grass 4 



Apparent ' exceptions to the distinguishing 



characters described 4 



INTRODUCTION. 



The close relationship of Sudan grass and Johnson grass leads to a 

 pronounced similarity in their seeds. The two kinds of seed can be 

 distinguished, however, when their comparative size and certain 

 features of their appearance due to differences in development are 

 considered. Oakley ^ and Vinall ^ have referred to these characters 

 as useful in distuiguishuig these two kinds of seeds. 



When properly interpreted, the distinguishing characters are 

 believed to be sufficiently reliable to make possible an accurate 

 quantitative analysis of a mixture of the two kinds of seed, even 

 though unhuUed grains of both grasses are present. 



When the seeds of the two kinds are under observation, the larger 

 size of the Sudan grass seeds, includuig the hulled grains, is readily 

 noticeable. The lighter color of the hulled grains is also evident. 



Distinguishing characters presented by either of the two kinds of 

 seed observable in the absence of the other depend chiefly on a 

 difference in the development of the plants preparatory to seed fall. 

 This may best be understood by first considering the structure of the 

 terminal clusters of the general seed clustc^r, or inflorescence taken 

 coUoctivrJy. One of these seed (dusters, shown in figure 2, illustrating 



> Oakley, K. A. Some new grasses for the South. U. S. Dept. Agr. Yearbook, 1912, p. 495-504, pi. 65-70. 

 1913. 

 2 \'iriall, If. N. U. S. Dept. Agr., Farmers' liul. 005, p. 15. 1914. 

 61990°— Bull. 40fi— IG 



