CH. VIII] 
“ SEED ’-CHARACTERS 
127 
America, Aristida hygrometrica in New Zealand, Hetero- 
pogon contortus in New Caledonia. 
The driving action of even small 
reflexed asperities on awns 1s well 
illustrated by the fruits of Hordeum, 
which are often made by children to 
creep up the sleeve. 
When we come to examine the 
external features of the “seeds” of 
grasses—usually the caryopsis en- 
closed in one or more pale, but 
sometimes in glumes as well—the 
following diagnostic characters are 
of importance. 
The size varies from lengths of 
2mm. or less (Poa, Aira) (Figs. 43, 
44) to 15—20 mm. or more (Arrhe- 
natherum) (Fig. 47) and distinction 
must be made between the various 
Fig. 43. 
Poa annua. 
d, the ‘*‘ seed,” nat. 
size; a and J, ditto, 
x about 7; ¢, cary- 
opsis, natural size 
(above) and x about 
7. Note the ribs 
and silky keel. No 
‘““web.” Nobbe. Cf. 
Figs. 54—56. 
characters of the caryopsis devoid of its coverings (palez, 
glumes) and such as really belong to the latter. 
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. 
In many cases the “seed,” consisting of the caryopsis 
closely compressed between the palez, is boat-shaped, e.g. 
