II. Match the words and word combinations in column a with their Ukrainian

equivalents in column B.

A B

1. quality a) властивість

2. fibre b) деревний сік

3. property c) серцевинні промені

4. sap d) заболонь

5. wood rays e) гнучкий

6. pith f) зовнішній шар

7. sapwood g) ядрова деревина

8. bark h) ріст, приріст

9. layer of wood i) внутрішній шар

10. tough j) серцевина (дерева)

11. flexible k) річні кільця

12. heartwood l) коріння

13. ring-porous wood m) порожнистий

14. annual rings n) розсіяно-судинна деревина

15. cell o) шар деревини

16. cell cavity p) клітина-порожнина

17. growth q) кільцесудинна деревина

18. roots r) клітина

19. hollow s) волокно

20. diffuse-porous wood t) кора

21. stem (trunk) u) якість

22. outer layer v) міцний

23. inner layer w) стовбур

III. Read and translate the following sentences.

1. Woods have different qualities.

2. All wood is made up of cells which are called fibres.

3. Lignin holds the fibres together.

4. Lignin makes the wood tough and flexible.

5. A tree consists of three parts.

6. Cell division in the cambium causes a tree to grow in thickness.

7. Wood rays serve to store food.

8. Softwoods do not have vessels.

9. In hardwoods wood rays are very definite.

10. The outer part of the bark consists of dead cells.

11. A new layer of wood is added to the tree every year.

12. Heartwood is darker than sapwood.

IV. Read and translate the text. Structure of Wood

Although woods from different trees have different qualities, all woods are basically the same, physically and chemically. All wood is made up of cells which , because they are long and narrow, are called fibres. These fibres may be from 1 mm to 8 mm long. A nonfibrous material, lignin, holds the fibres together and makes the wood tough and flexible. Cells in dry wood are usually hollow, which makes the wood light in weight and effective as heat and sound insulation. The cells are arranged parallel to each other along the trunk of a tree. Woods with very small cell cavities are hard and difficult to work. Dry wood is mainly composed of cellulose, lignin and hemicellulose. Cellulose, the principal component, is composed of carbon, hydrogen and oxygen. It makes up about 50 percent of wood substance by weight. About 16 to 33 percent is lignin which although made up of the same elements as cellulose, is different in its properties. In addition, other substances, such as minerals, sugars, resins, dyes, starches, oils and gum, are found in wood.

The structure of wood. A tree consists of three parts: the roots, the stem (trunk) and the crown. A cross-section of a tree trunk shows wood structure (from outside to center): bark, which may be divided into the outer dead part and the inner thin living part. Then there is a thin layer of cells which is called cambium. Cell division in the cambium causes the tree to grow in thickness.

Next comes sapwood – light-coloured wood. Sapwood contains both living and dead cells. Its function is to store food and transport sap. Sapwood gradually changes into heartwood. The cells of heartwood are inactive, they do not take part in the life processes of the tree. Heartwoods may contain various substances, such as phenolic compounds, gums, resins and others, which makes it more decay resistant than sapwood. Heartwood is usually darker in colour than sapwood. In the center of a tree stem there is a pith.

Medullary, or wood rays. Wood rays are rows of cells that are oriented horizontally in the direction from pith to bark. The rays serve to store food and transport it horizontally in the tree. In hardwoods, the rays are clearly defined. In softwoods they can be seen only with a magnifier.

Pores, or vessels. Vessels are tubes which are made up of large cells. They conduct sap from the roots to the leaves. Wood of our common trees can be divided into two groups: porous and non-porous. Softwoods do not have vessels. The porous woods are subdivided into ring-porous and diffuse-porous.

Annual rings, or growth rings. These are concentric layers of wood which are added during each growing season to the diameter of the trunk. The rings are usually

1 – Bark

2 – Cambium

3 – Sapwood

4 – Heartwood

5 – Pith

6 – Wood Rays

7 – Annual (growth) Rings

Fig. 1. Tree Cross-Section

very easy to see because in the temperate climates, the wood which is formed in

spring, is different from the wood formed late in the season. The wood which is formed in spring when growth is more rapid, is called earlywood, or springwood. It is characterized by cells which are larger and thin-walled making a rather porous layer of wood. Slower growth late in the growing season produces latewood, or summerwood. It has smaller thick-walled cells and forms more dense wood. By counting annual rings we can tell the age of the tree. In many tropical regions where growth may be practically continuous all the year round, trees usually do not have annual rings.