The vascular bundles in the stems of most of dicots are conjoint,collateral and open. In each of these bundles

• A
  Xylem and phloem are on the same radius with phloem towards the pith and xylem towards the pericycle without a strip of cambium between them.
• B
  Xylem and phloem are on the same radius with xylem situated towards the pith and phloem situated towards the pericycle and a strip of cambium separates the two.
• C
  Xylem completely surrounds the phloem on all sides but the two are separated by the cambium.
• D
  Phloem completely surrounds the xylem and a strip of cambium separates the two.