Scanning electron micrograph of winter's bark (Drimys winteri) pollen. The pollen is found in associations of 4 grains,known as tetrads. The grains are not pressed together closely in the tetrad. The outer wall (exine) of the grain comprises rod-like processes (bacula),fused at their tips,forming a network of ridges (muri) and surrounding a circular germinal pore. When the pollen,containing male gametes,lands on the stigma of a flower,it germinates. A pollen tube grows out of a pore,down the stigma,to the ovary. Male nuclei pass down the tube and fertilize the ovules to form seeds. Magnification: x2275 at 10x8 inch size | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library |
Bildgröße: | 3167 px × 3996 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |