Fig. 17.3-1a and b. Transverse section of ivy stem with lenticel (Hedera helix). Most of this stem is covered with ordinary cork – the cells fit together so tightly that oxygen movement is not possible. But at the lenticel, the cork cells have very small intercellular spaces that permit oxygen diffusion into the living layers of the inner bark and secondary phloem, the vascular cambium, and the sap wood.

            In the high magnification view, the complementary cells are visible, but the intercellular spaces are not – even at your own microscope at high power, you will probably not be able to see them.

            As subsequent cork cambia form deeper inside the stem, they will form lenticels in the same region as the pre-existing lenticels – there will be an oxygen diffusion pathway through all layers.