pollen grain

It depends on whether you are talking about animals or plants. In plants it is a pollen grain (microgametophyte) and in animals is a sperm (spermatozoa)

Unlike seedless vascular plants gymnosperms do not require water to transport the sperm. Instead a partly developed microgametophyte (pollen grain) is transferred to the viscinity of the megagametophyte (female) passively by the wind this process is called pollination. After pollination the endosporic microgametophyte produces a pollen tube and drops the sperm into the female ovary (i believe this is called pollination drop).

it depends on gymnosperm (naked seed) or angiosperm (flowering plant) this is the angiosperm - Another germination event during the life cycle of gymnosperms and flowering plants is the germination of a pollen grain after pollination. Like seeds, pollen grains are severely dehydrated before being released to facilitate their dispersal from one plant to another. They consist of a protective coat containing several cells (up to 8 in gymnosperms, 2-3 in flowering plants). One of these cells is a tube cell. Once the pollen grain lands on the stigma of a receptive flower (or a female cone in gymnosperms), it takes up water and germinates. Pollen germination is facilitated by hydration on the stigma, as well as the structure and physiology of the stigma and style.[1] Pollen can also be induced to germinate in vitro (in a petri dish or test tube).[3][4] During germination, the tube cell elongates into a pollen tube. In the flower, the pollen tube then grows towards the ovule where it discharges the sperm produced in the pollen grain for fertilization. The germinated pollen grain with its two sperm cells is the mature male microgametophyte of these plants.[1

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