(2) The heavy snow overwhelms the pine trees, which are tall and straight, and the pine trees in the poem are gymnosperms;
(3) The next day, the lotus leaves are infinitely green, and the lotus flowers in the sun have different colors. The lotus in the poem belongs to angiosperms;
(4) When I was in Qiu Lai on September 8th, I killed a hundred flowers. The description in the poem is that chrysanthemum belongs to angiosperms.
So, the answer is: (1) algae; (2) gymnosperms; (3) angiosperms; (4) Angiosperms.