SEED CHARACTEES OF SUDAN GEASS AND JOHNSON GEASS. 5 



Some of the seeds of Johnson grass present a short stem (fig. 5, a), 

 owing to failure to separate at the articulation of the rachis and spike- 

 let. In such cases, the distinct suture at the articulation in Johnson 

 grass (fig. 5, h), evident under a good magnifier, appears to be an 

 unfailing mark of distinction between the seeds of Johnson grass and 

 Sudan grass. Corresponding with the occurrence of stem-bearing 

 seeds, some of the former seeds show incomplete, broken appendages, 

 similar to those which occur in the latter. 



In the seeds of both Sudan grass and Johnson grass some indi- 

 viduals have a stem from one to three times as long as the seed 

 (fig. 5, c). This is the portion of the branch immediately below the 

 seed cluster, and the seed is the lowest one of the cluster. It will 

 be observed in figure 5 and also in figure 2 that this branch is con- 

 tinued past the first spikelet without an evident suture (fig. 5, d). 

 A partial suture for this first spikelet of the cluster does occur, how- 

 ever, at the base of the spikelet and is evident on the side of the axis 

 opposite that shown in the figure, where it has the appearance 

 shown in figure 5, h. 



Examination of various samples of Sudan grass and Johnson 

 grass seeds has shown the combined characters of size of seed in 

 the hull, the presence or absence of the articulating suture, and 

 finally" the size, form, and color of the grain, including the relative 

 size of the embryo (compare fig. 3, e, and fig. 4, d) to be conclusive 

 points of distinction. 



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