The nut of the acorn grows from a woody cup, which may remind you of a hat. The small scales that make up the cup may be thin and flat, or thick and forming wart-like growths (tubercles). This variation is a great start for narrowing down the possible species. All oaks native to North America and Europe have a spiral of overlapping scales on the cup. Some (but not all) East Asian oaks have scales that form concentric rings instead. These are called ring-cupped oaks, and belong to the Cyclobalanopsis subgenus. Acorns come in many shapes, but you can divide them into two rough groups. Some are round ("globose"), or nearly round with a blunt tip. Others are elongated ("ovoid" or "oblong") and usually taper to a point ("fusiform"). The acorns of some species have parallel ridges (striations) running between the two points. This can vary within one species, so a smooth acorn isn't always diagnostic. Mature acorns can be light brown, dark brown, black, or chestnut red. If the acorn is still green or greenish-grey, it probably fell off the tree early. Acorns range in size from nubs less than ½ inch (1.25 cm) long, to behemoths the size of your palm. Most acorns within a single species and region are similar in length within about ½ inch (1.25 cm). One important exception is the cork oak of the Mediterranean, which drops large acorns in autumn and a smaller batch in winter.  The size and shape of the cup is also useful, and you can easily eyeball it by comparing it to the nut. For example, the Northern red oak has a cup that sits flat at the top of the nut, while the overcup oak and bur oak wrap almost the entire nut in a cup. The length of the stalk the acorn grows on can also help identification. The cup of some acorns have hairs on the inner and/or outer surface. You can also look for hairs on the inner surface of the shell, after cracking it open. Botanists describe this hairy material with these terms:  Woolly: long, matted hairs. Some species only have hair near the tip of the acorn, so check there. Pubescent: short, fine hairs. Glabrous: smooth. If an acorn on the ground is sprouting through its shell, it must belong to a species that germinates at this time of year. In North America, oaks are divided into white oaks, which sprout in fall right after the acorns drop, and red oaks, whose acorns spend the winter dormant and sprout in spring.  Here, we're talking about the white and red oak categories. These include the specific species "white oak" and "red oak," but there are many more possibilities. Most acorns lose their cup before sprouting. The Asian ring-cupped species are the main exceptions.
افحص قشور غطاء الجوز. انظر لشكل الجوز. تفقد اللون. قس الثمرة. ابحث عن الشعيرات. ابحث عن الجوز المنبت.