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Selecting and B l v i n g Sutable W o o d

Hardwood cells pjfc_re

parenchyma (storage cells)

encountered beautiful, aromacie, light and easily worked woods in common use, and wich che restoration of che monarchy in 1660 inrroduced pine, fir and sprucc woods for consrrucrion and carving. The imporcers who brought these timbers in wcre sclling woods thac were soft by comparison wich oak and che othcr commonly uscd nacive timbers. They becamc known as softwood importcrs and che namc has stuck.

Botanical Classification and Cell Structure

1l was only later rhat raxonomists classified rhe plants according to their ways of producing flowers and fruic. The needle- and scale-leaved trees were found to bclong to one group, the gymnosperms, which means having, literally, naked sccds. The broad-leaved trees belong to the angiosperms, which have secds in vcssels. Softwoods are morÄ™ primitive than hardwoods, having a less sophisticated cell structure composed mainly of cigar-shapcd cells called tracheids which conduct the sap in a zigzag fasliion through connecting holes or pits in their walls and also provide strength. Softwoods contain very smali rays and often have resin canals or ducts (Fig 2.11). Hardwoods, on the other hand, are principally madÄ™ up of vessels which are short, hollow cells stacked one above the other to form a sort of pipÄ™ system, fibrcs which are dense, elongated cells and are morÄ™ abundant in the latewood, and tracheids. Hardwood rays are usually visible to the naked eye and may be a millimetrc or morÄ™ thick and several centimetres high. The hardwoods may also contain gum, resin or latex ducts. Both types of tree have a certain amount of vcrtical storage cells (axial parenchyma). Yew and balsa, by these criteria, are respecrivcly a hard softwood and a soft hardwood. Gingko (Gingko biloba) is an exception to the broad-leavcd rulc, having a fan-shaped leaf but being a primitive life form with the same physiology as softwoods.

Incidentally, a common mistake is to think that

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