. Essentials of biology presented in problems. Biology. Cross section of a young taproot: u, u, root hairs; b, epidermis; c, cortex; d, fibrovascular cylinder or wood. Root Hairs. — Careful examination of the root of one of the seed- lings of mustard, radish, or barley grown in the pocket germinator shows a covering of tiny fuzzy structures. These structures are very minute, at most 3 to 4 mm. in length. They vary in length according to their position on the root, the most and the longest root hairs being found near at the point marked R. H. in the Figure. These structures are outgrowths of th
. Essentials of biology presented in problems. Biology. Cross section of a young taproot: u, u, root hairs; b, epidermis; c, cortex; d, fibrovascular cylinder or wood. Root Hairs. — Careful examination of the root of one of the seed- lings of mustard, radish, or barley grown in the pocket germinator shows a covering of tiny fuzzy structures. These structures are very minute, at most 3 to 4 mm. in length. They vary in length according to their position on the root, the most and the longest root hairs being found near at the point marked R. H. in the Figure. These structures are outgrowths of the outer layer of the root (the epi- dermis), and are of very great im- portance to the living plant. Structure of a Root Hair. — A single root hair examined under a compound microscope will be found to be a long, round structure, almost colorless in appearance. The wall, which is very flexible and thin, is made up of cellulose, a substance somewhat like wood in chemical com- position, through which fluids may easily pass. If we had a very high power of the microscope focused upon this cellulose wall, we should be able to find under it another structure, far more delicate than the cell wall. This is called the cell membrane. Clinging close to the cell membrane is the protoplasm of the cell. The interior of the root hair is more or less filled with a fluid called cell sap. Forming a part of the living protoplasm of the root hair, sometimes in the hairlike prolongation and some- times in that part of the cell which forms the epidermis, is found a nucleus. The protoplasm, nucleus, and cell membrane are alive; all the rest of the root hair is dead. Young embryo of corn, show- ing root hairs (R. H). and growing stem (P.).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George William, 1873-1948. New Y
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
