60 SEEDS AND FRUITS 
In structure these seeds differ from those of the Bean type in 
that they have three distinct parts, an embryo, endosperm, and 
seed coat, but in number of cotyledons, which is two, the two 
types are identical. Since endosperm is present, the seeds of 
this type are known as albuminous seeds. (Fig. 65.) Although 
some endosperm is always present, sometimes, however, much 
of it is absorbed by the embryo during the development of the 
seed, and in this case the cotyledons, which are comparatively 
free from stored food in 
many of these seeds, as- 
sume some importance as 
storage organs, though not 
so much as in the Bean 
type. In the Buckwheat 
family, represented by 
Buckwheat, Rhubarb, 
A B Docks, and Smartweeds, 
lic. 65.— A, section through a Potato and also in some plants 
seed. c, embryo; v, endosperm; ¢, testa. of the Goosefoot family, 
B, section through an achene of Buckwheat. ¢he hardened ovary wall 
em, embryo; e, endosperm; 0, ovary wall j 
and testa. Enlarged. 
which, when mature re- 
sembles a seed coat, per- 
sists as an outer covering over the seed, thus forming with the 
seed a fruit-like structure known as an achene, a term which is 
applied to many hard, usually one-seeded fruits, that do not dehisce 
or, in other words, that do not open to allow the seed to escape. 
In external characters, seeds of this type present various differ- 
ences by means of which one can usually identify the family and 
often the species to which the seed belongs. Those most com- 
mon in our region range in size from the smallest of the Dodder 
seeds, which are almost dust fine, to the size of the Castor 
Bean. The shape, which in many cases is the chief character by 
which the family and often the species to which the seed belongs 
is identified, may be globular, oval, flat, or angled. Such colors 
as red, yellow, brown, and black are common and serve along 
with shape and size as a means of identifying different seeds. 
Sometimes the seed coat is much roughened, as in the Cockle, 
and in some cases, as in the Milkweeds, the seed coat develops 
hair-like appendages. 
In case of Flax, Buckwheat, Coffee, and the Castor-oil plant, 
