The caryopsis proper may be short and stout and devoid of a groove--“Millet-seed” type (Fig. 45)--but is oftener elongated, like a grain of Wheat, and then has the characteristic longitudinal groove on the face opposite that where the embryo is situated (Fig. 46). Details of shape--e.g. cylindroid, fusiform, flattened, &c.--are also of diagnostic value. [Illustration: Fig. 43. _Poa annua. d_, the “seed,” nat. size; _a_ and _b_, ditto, × about 7; _c_, caryopsis, natural size (above) and × about 7. Note the ribs and silky keel. No “web.” Nobbe. Cf. Figs. 54-56.] In many cases the “seed,” consisting of the caryopsis closely compressed between the paleæ, is boat-shaped, e.g. _Lolium perenne_, _Festuca elatior_. If this “boat” is long and narrow it may be termed barge-shaped, e.g. _Brachypodium sylvaticum_, &c. (Figs. 71, 72): if short, broad, and open or shallow, the term coracle-shaped seems to apply, e.g. _Bromus arvensis_ (Fig. 73). [Illustration: Fig. 44. _Aira cæspitosa._ The minute “seed” (nat. size) is seen to the right, and the caryopsis (nat. size) to the left of _c_, the caryopsis, × 8. _a_ and _b_, the “seed,” × 10. The basal awn is about as long as the palea, and the rachilla is very hairy. Nobbe.] [Illustration: Fig. 45. _Phleum pratense._ Millet-seed type. _a_, “seed,” nat. size; _b_, ditto, × about 7; _d_, caryopsis, nat. size; _c_, ditto, × 7. The rounded caryopsis in _b_ is only loosely covered by one palea. Nobbe.] [Illustration: Fig. 46. Boat-shaped “seed” of _Glyceria fluitans_. _a_, nat. size; _b_ and _c_, × about 6. _d_, caryopsis, × about 10. Note the 5-7 strong nerves, and the slender cylindrical rachilla. Cf. Figs. 57 and 58. Nobbe.] [Illustration: Fig. 47. _Arrhenatherum avenaceum._ The “double seed” (_a_ and _b_) consists of two pairs of paleæ with their enclosures. The lower pair (γ) are devoid of fruit, and the outer palea has a long twisted and kneed basal awn: the upper pair (β) enclose the fruit, and the palea has a short straight awn. Note the stiff basal hairs. _a_, nat. size; _b_, × about 6; _c_, caryopsis, nat. size; _d_, ditto, × 6. Nobbe.] [Illustration: Fig. 48. _Lolium temulentum._ Type of boat-shaped “seed” with sub-terminal awn arising from between two teeth. _c_, “seed,” nat. size; _a_ and _b_, ditto, × 6. Note the large smooth rachilla. Nobbe. Cf. Fig. 57.] Further important distinctive characters are obtained from the absence or presence of awns, and the peculiarities--length, stiffness, &c.--of the latter. The awns may be straight, hooked, or kneed (i.e. sharply bent); twisted or not; smooth or serrulate. They may be inserted at the base or near the middle of the back of the investing palea, or glume, or near its apex, as indicated by the terms basal, dorsal, sub-terminal (see Figs. 47-50).