UNITED STATES DEPARTMENT OF AGRICULTURE 
I BULLETIN No. 406 
iC^'^3^ WM. A. TAYLOR, Chief J&?*$&L 
Contribution from the Bureau of Plant Industry 
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. 
Introduction 
Distinguishing characters of the seeds of 
Sudan grass 
CONTENTS. 
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 1 and Vinall 2 have referred to these characters 
as useful in distinguishing 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 unhulled grains of both grasses are present. 
When the seeds of the two kinds are under observation, the larger 
size of the Sudan grass seeds, including 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 cluster, or inflorescence taken 
collectively. One of these seed clusters, shown in figure 2, illustrating 
1 Oakley, R. A. Some new grasses for the South. U. S. Dept. Agr. Yearbook, 1912, p. 495-504, pi. 65-70. 
1913. 
2 Vinall, H.N. U. S. Dept. Agr., Farmers' Bui. 605, p. 15. 1914. 
51990°— Bull. 406—16 
