Lesson 1

The structure of seeds

The Structure of a Bean Seed. Let us first study the structure of a bean. It is rather large and all its parts are easily discernible. One has to know the structure of this seed. The seed of a bean is covered on the outside with a solid smooth shiny membrane — the seed coat. There is a little elongated scar on the seed coat, the hilum. This is the trace of the small stalk by which the seed was attached to the inside of the bean-pod. The solid membrane of the bean seed protects the tender parts of the seed from possible injuries.

When the skin is taken off the seed we see that this latter consists of two lobes or cotyledons. The lobes are connected with one another by a small body, which under the magnifying glass displays: a rootlet, a small stem, and a small bud with tiny leaves. These rootlets stem and bud together with the cotyledons form the embryo of the plant.

The Structure of a Wheat Seed. Seeds of wheat differ considerably from bean seeds. Firstly, the thin membrane tightly adheres to the inside of the seed. It cannot be separated from the seed even after soaking it in water.

A small embryo is located in the seed with a rootlet, or radicle, and a leaf bud. If we remove the embryo of the seed we find a small scale by means of which the embryo is attached to the remaining part of the seed. This scale is a cotyledon which is called shield. It is different from the juicy cotyledons of the bean.

The remaining part of the seed is filled with a uniform floury mass, the albumen, or endosperm. The endosperm contains nutritious substances which during the germination penetrate through the shield into the embryo of the seed. In all grain plants the stored-up nutritious material passes from the endosperm to the developing embryo by way of the cotyledon-shield.

The main difference between the seed of the bean and that of the wheat consists, therefore, in the following: in the bean seed the nourishing substances are contained in the cotyledons, while in the wheat seed they are contained in a special part of the seed, the endosperm. The bean seed has two cotyledons, the wheat seed one. In most of our plants the seeds resemble in the main either the seed of the bean (for instance, seeds of peas, lentils, cucumbers, pumpkins), or that of wheat (seeds of rye, oats, maize, etc.).

Words and word combinations to be learnt:

adhere, v	прилипать, приставать; твердо держаться
bean-pod, n	стручок бобовых
cotyledon, n	семядоля
contain, n	содержать
cucumber, n	огурец
dissolve, v	расстворяться
drought, n,	засуха
elongate , v	удлинять (ся)
embryo, n	зародыш
endosperm , n,	эндосперм
floury, a	мучной, мучнистый
germination, n	прорастание
hilum, n	рубчик семени
lentil, n	чечевица
lobe, n	доля, долька
maize, n	маис, кукуруза
moisture, n	влага, влажность
oat, n	овес
pea, n	горох
penetrate, v	проникать
pulpous, a	пульпообразное
pumpkin, n	тыква
radicle, n	корешок
resemble, v	походить, иметь сходство
rootlet, n	корешок
root system,	корневая система
rye, n,	рожь
saturate, v	насыщать
seed coat, ,n	оболочка семени
shield, n	щит, щиток
soaking, n	замачивание (семян); впитывание, всасывание