SEEDS or QUACK-GBASS AND OF CERTAIN WHEAT-GKASSES. 



Quack-grass and the wheat-grasses are closely related botanically, 

 belonging to the same genus, Agropyron. The wheat-grasses com- 

 monly appearing in brome-grass seed are slender wheat-grass (Agro- 

 pyron tenerum Vasey) and western wheat-grass (Agropyron occidentale 

 Scribn.),'* known also in the West as Colorado bluestem. 



Owing to the close relationship of these grasses, their seeds, taken 

 individually at least, appear to be practically indistinguishable. The 

 structure and fruiting habits of the seed clusters, however, afford, 

 means for their recognition which appear to be well founded. 



NATURE OF THE SEEDS OF AGROPYRON. 



The individual seeds, or ripened florets, of Agropyron are produced 

 in clusters termed "spikelets," each spikelet containing several seeds. 

 At maturity the spikelets usually tend to break apart, permitting the 



seeds to separate. Xot all the spike- 



_^, - iS v;.^ lets thus wholly go to pieces, but 



■•: some appear in their entirety or in 



'- part in samples of seed. Thus, the 



term "seed," as popularly employed^ 



refers in this case both to whole or 



partial spikelets and to individual 



seeds. 



The complete spikelet (see fig. 

 1, a) consists of a pair of oppositely 

 placed, somewhat unequal, slender 

 scales, or glumes (d and e), united 

 at the base of the spikelet, and sev- 

 eral alternately arranged "seeds,'' 

 or ripened florets, situated between 

 and above the glumes. The glumes 

 are united side by side or on the 

 same level, which is a readily ob- 

 served mark of distinction in spike- 

 lets of Agropyron. They are more 

 or less distinctly veined length- 

 wise, the veins varying from three 

 to seven in the kinds under consideration. The variation in size and 

 form of spikelet and in form, venation, etc., exhibited in the glumes 

 of these kinds of Agropyron affords marks of distinction. 



The individual seeds (see fig. 1, h and c), or ripened florets, consist 

 of the grain inclosed between two scales, one of which, the lemma, is 



a Agropyron ocddentale Scribn. is described in the seventh edition of Gray's Manual 

 under A. smithii Rydb., and in Britton's Manual under A. spicatum (Pursh) Scribn. 

 and Sm. 



[Cir. 73] 



.^f 



Fig. 1.— a spikelet and seeds of quack-grass, 

 showing the general structure of the spike- 

 lets and seeds of Agropyron: o, A complete 

 spikelet; 6, the inner face of a seed, showing 

 the grooved palea and the rachilla segment 

 (/); c, a seed, showing the rounded back of 

 the lemma; d and e, glumes of the spikelet. 

 (Enlarged.) 



