CBSE Class 10 Science 2017 · Paper 31/1/1/C · Question 23

(a) Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. Its two types are (1) self-pollination, in which the pollen reaches the stigma of the same flower, and (2) cross-pollination, in which the pollen is carried from one flower to the stigma of another flower of the same species, usually on a different plant, by agents such as wind, water or animals. (b) The diagram shows the pistil in longitudinal section with pollen grains on the stigma. From one grain a pollen tube grows down through the style into the ovary and enters an ovule. Labelled: (i) stigma, at the top of the pistil; (ii) pollen tube, with a male germ cell inside it near its tip; (iii) female germ cell (egg), inside the ovule.