What helps to bring pollen grains to the stigma

it is very complex process but it can be easily done by natural means like birds bees

When insects such as butterflies sit on the anther (where pollen grains are produced) and then fly to the stigma with the pollen grains stuck on them. Another type is when wind is coming strongly it (pollen grains)flies to the stigma, which helps in pollination.

Pollen tube helps to transfer pollen grains to stigma

• It is carried out by cross-pollination by agents like insects,wind and sometimes even water.
• Firstly in few of the plants, the stigma is quite sticky and is wide open in the case of wind pollination. While in the case of insect pollination, the plants are normally bright,have juicy nectar and have sweet scent. Thus, the insects get attracted and the pollen is stuck on their and is transferred to another plant which has female parts in the flower.
• Thereby, the pollen grains get transferred to stigma in cross and self pollination.

Hope this helped!

bgb

by wind  ,  air , water

pollination
 

the insects like butterflies carry the pollen to the stigma of a flower of the same kind

There are different ways of pollination, some are

1} Pollination by insects 
2} Pollination by wind
3} Pollination by water
4} Artificial pollination

insects such as bees sit on top of the flower that time the pollen gets stuck on their legs and when they shift yo another flower they gets transfered easy!;)