16 THE SEEDS OF THE BLUEGRASSES. 



The caryopsis corresponds to an individual grain in wheat, rye, and 

 barley, and consists almost entirely of the seed proper, to which is 

 added onl}- the thin wall of the seed vessel. This is intimately blended 

 with the seed coat, the two forming the covering- of the true seed. 

 The caryopsis is spindle-shaped and often broadest between the middle 

 and the base. It is often bluntly keeled along one face and more or 

 less evidently grooved along the opposite face. In the commercial 

 bluegrass seeds the grain is amber-colored or dull wine-colored and 

 semitranslucent. The surface is finely granular and dull. The kernel 

 of the seed forms that part of the grain within the seed and seed- 

 vessel walls. It consists of the embryo and endosperm, the latter 

 forming the greater part. The embr3^o is situated at the basal 

 extremity of the grain and is evidejit externally as a small ridge, often 

 within a slight depression, on the keeled face. The grain adheres 

 along its grooved face to the palea in some species in which free grains 

 are not common in well -cleaned commercial seed. 



The two chaffy scales of the floret differ chiefly in size, form, rela- 

 tive position, venation, and texture. The larger one, called the flower- 

 ing glume or simph" the glume, incloses the edges of the other, termed 

 palea. The grain rests between the glume and palea, its keeled face 

 13'ing against the glume. The rachilla segment is at the base of the 

 palea and opposite the glume. It is one of the articulating sections of 

 the rachilla, or axis of the spikelet. 



The characters by which the different kinds of bluegrass seeds are 

 distinguished one from another are afforded by the glume, palea, and 

 rachilla segment, and involve size, form, color, veins of the glume, 

 form and texture of the apex of the glume, and the pubescence. 



The glume is stiffish and more or less pointed at the ends. Its base 

 is marked by the presence of a small, somewhat knob-like appendage, 

 the callus. The latter bears the scar of attachment of the floret and, 

 in certain species, a more or less pronounced tuft of webb}" hairs. 

 The back of the glume is more or less keeled along its longitudinal 

 center. Besides the fold forming the keel, the edges of the glume are 

 infolded along the marginal veins. The marginal folds often are most 

 pronounced within and sometimes are contined to the lower half of the 

 glume, in which event the upper margins usually diverge and become 

 spreading or flaring at the apex. The keel is strongly arched length- 

 wise in some species and in others is nearly straight. Five veins 

 traverse the glume longitudinally; one occupies the keel, two are at 

 the marginal folds and are termed the marginal veins, while the other 

 two are situated midway between the keel and marginal veins and are 

 called intermediate or, l)y some authors, lateral veins. The interme- 

 diate veins exhibit considerable variation in distinctness in the differ- 

 ent species. The vei^i occupying the keel extends to the apex. The 

 apex and often the upper part of the lateral margins of the glume in 



