Herbaceous dicot vine: Cucurbita

long section: Cucurbita stem magnification: 100x Phloem consists of large clear sieve tubes with pitted cell walls and sieve plates and small narrow green stained companion cells. Many sieve plates have deposits of a mucoid p-protein that forms as part of the trauma response in injured phloem. Between the xylem and phloem are a few regularly arranged layers of elongated cambium cells.