### gametophytes:

Pollen grain
* All pollen grains develop initially in groups of four called tetrads.
* Every pollen grain contains sperm nuclei, which fertilize the ovules in the female flowers.
* Many pollen grains develop inside each pollen sac.
* Most pollen grain comes from flower plants
  - in contact
* Most pollen grain contains kernels
  - nutrients
* Most pollen grain has circular pores
  - functions
* Most pollen grain has small circular pores
  - surfaces
  - is produced by plants
* Most pollen grains are too large to exhibit noticeable Brownian motion
  - preserve well once they have settled at the bottom of a water system
* Some pollen grain becomes gametophytes
  - male gametophytes
* Some pollen grain contains female gametophytes
  - immature male gametophytes
* Some pollen grain enters cones
  - female cones
  - young female cones
* Some pollen grain has projections
  - protective walls
  - spikes
  - wings
* absorbs water from stigma by osmosis.
* are capable of producing sperm, the male sex cells
  - captured in watery droplets exuded by each ovule
  - carried to stigma of another flower
  - covered with a tough coat containing sporopollenin
  - found on the anther, which is at the end of the filament
  - large, and, they tend to adhere to each other even in dry weather
  - male gametophytes carried by wind, water, or a pollinator
  - multicellular and constitute the Microgametophyte
  - nonsaccate
  - of inestimable value in the bee household
  - one among the factors responsible for triggering allergic diseases
  - rather small and their surface is smooth
  - released from a flower
  - so small that they easily can pass through the tightest window screens
  - the immature male gametophytes existing in seed plants
* are the male gametophytes in flowering plants
  - reproductive cells of flowering plants
  - seeds or reproductive cells of flower blossoms
  - small male reproductive bodies of plants that fertilize female flowers
  - tiny male reproductive bodies of flowering plants
  - tiny, yellow, dustlike particles found inside flowers
* are transferred pollination
  - to the stigma of the same flower
  - tricolpate, or a modification thereof
* begin to germinate before pollination.
* can become trapped underneath lenses
  - land and germinate anywhere along the length of an exposed silk
* carry the male genetic information for fertilization.
* come from seed bearing plants
  - in many shapes and sizes, depending on the species of plant
* contain male gametophytes, the tiny haploid stage that makes the sperm
  - sperm that fertilizes the egg in the ovule
* contain the male gametes in sexually reproducing plants
  - two cells, one of which forms a pollen tube with two sperm cells
* develop in the anther , a sac at the top of each stamen.
* dicolporate, shed as monads, tricellular at dispersal.
* ellipsoidal when dry, and spherical when moistened.
* enter a young female cone and then rest for one year.
* germinates on the stigma and begins to form a pollen tube which extends into the ovule
* give the anthers a dusty appearance when the anthers have released pollen.
* have a thick protective wall
  - distinctive shapes, so they are useful for identifying plants
  - two very important attributes
* hold amino acids, starch, oil, and other nutrients.
* inaperturate, shed as monads, bicellular at dispersal.
* is gametophytes
* possess such a coat, which is made of a very strong material called sporopollenin.
* present a variety of challenges to study and interpret under the microscope.
* preserved in bogs provide clues to past vegetation and climate.
* reach, the surface of the stigma.
* released by the anther are picked up by visiting insects or the wind.
* sift down between the scales of the female cone and are drawn into the micropyle.
* trisyncolporate, shed as monads, bicellular at dispersal.