Reproduction

To determine the correct set of statements about Phaeophyceae, let's analyze each statement:

• Asexual reproduction:
  A. Asexual reproduction occurs usually by biflagellate zoospores.
  This statement is correct as members of Phaeophyceae typically reproduce asexually via biflagellate zoospores.
• Sexual reproduction:
  B. Sexual reproduction is by oogamous method only.
  This statement is incorrect as sexual reproduction in Phaeophyceae can occur by isogamous, anisogamous, or oogamous methods, not solely by oogamous methods.
• Stored food:
  C. Stored food is in the form of carbohydrates which is either mannitol or laminarin.
  This statement is correct as mannitol and laminarin are the main forms of stored carbohydrates in Phaeophyceae.
• Pigments:
  D. The major pigments found are chlorophyll a, c, carotenoids, and xanthophyll.
  This statement is correct because these pigments are characteristic of Phaeophyceae.
• Cell structure:
  E. Vegetative cells have a cellulosic wall, usually covered on the outside by gelatinous coating of algin.
  This statement is correct as the cell wall in Phaeophyceae is typically composed of cellulose and algin.

Evaluating these statements leads us to conclude that the correct set of statements is: A, C, D, and E.

Therefore, the correct answer is: A, C, D and E only.