ANOTHER flower.Pollination is the first step of sexual fertilization in flowering plants. Pollen grains contain the male gamete, which is found in the anthers of the flower.Pollination may be of two types: self-pollination and cross-pollination. Self-pollination found when the pollen from the anther is TRANSFERRED on the stigma of the same flower, or another flower on the same plant. In Cross-pollination pollen transfers from the anther of one flower to the stigma of another flower on a different flower of the same species.Contrivances for cross-pollination - herkogamy, heterostyly, etc.Explanation-Herkogamy is the cross-pollination type in which the flower is of such structure that even being bisexual, the pollen grains fail to reach the stigma.There may be a mechanical barrier between the compatible pollen and stigma.So that self-pollination is not possible or there may be a hood-like covering that covers the stigma.In such a condition, only cross-pollination is possible. An example is Calotropis.Thereby herkogamy is found in Calotropis.Contrivances for cross- pollination-Cleistogamy is automatic self-pollination that takes place in closed flowers. So this process is the transfer of pollen grains from anthers to the stigma of the same flower, which is found in unopened flower. For example Cardamine and Commelina.Allogamy is also a cross-pollination type. In this type of pollination, pollen is transferred from the anther to the stigma of another plant of the same or different species. Allogamy may be of the following type- dicliny (UNISEXUALITY), dichogamy, herkogamy.Dichogamy is the cross-pollination type when the stigma and anther mature at different times. Either stigma becomes receptive before anthers DEHISCE (protogyny) or anther dehisces before the stigma becomes receptive (PROTANDRY).