Angiosperm, to which the largest flowers belong is:

Explanation

Rafflesia is a specialized total root parasite as the vegetative parts of its body are reduced the whole body is within the host root and the only structure that is visible outside, is the biggest flower. The diameter of the flower is one meter and its weight is about 10 kg. Its pollination is done by elephants. The flowers are fleshy white and they emit a smell, which resembles the smell of decaying meat.