The Epidermis is in direct contact with the external environment. It contains many important adaptations which allow plants to survive & reproduce on land. We will observe the most general adaptations as well as some exotic ones. The functions of many types of epidermal cells are well known but there are some specialized cells with unknown functions. The epidermis is important in both vegetative and reproductive organs. It is treated here in a broad sense as the superficial layer (or rarely layers) on all differentiated parts of the plant in the primary state of growth. During secondary growth the epidermis is often replaced by Periderm.

Many features of the epidermis can be seen in whole mounts at low magnification with the compound microscope.


Note the differences between the upper and lower surfaces as well as the veins vs the lamina.You may be able to use the 10X objective but be careful NOT to bring it into contact with the leaf. THICK paradermal (parallel to the surface) sections or peels may be needed to observe epidermis from stems because of their thickness.

I learned to do this by accident!!!!!!!!

Epidermal Peels: Epidermal features can also be captured by making peels. In many plants, particularly succulent ones, the epidermis may be easily stripped from fresh leaves. Such epidermal peels are useful for the study of the shape of epidermal cells and their arrangement as well as the distribution and structure of stomata. To make epidermal peels you should do the following.

  • Make a clean cut at one end of the structure.

  • Paradermal Sections: If the epidermis is not easily peeled, thin sections cut parallel with the leaf surface (paradermal sections) may be used. The latter will be demonstrated but are hard to do.

    Epidermal Windows: There is a method of looking at the epidermis of leaves that I call the window method.

    Epidermal Replicas: Finally, it is possible to make replicas of the Epidermis with Nail Polish. This works well with a smooth epidermis like Agave or Rhoeo but may not work well with highly pubescent one.

    I learned this particular procedure from an undergraduate!!!!!!!


    The Cuticle is a complex waxy layer secreted by Epidermal cells. It forms a barrier to water loss and the entrance of pathogens. Because it is waxy, it will stain with Sudan dissolved in ethanol.

    Leaves of Dicots:

    Leaves of Monocots:

    What do the polarizers indicate regarding the ORGANIZATION of the ergastic substance?

    In what part of the cell is it probably located?

    What might be the function of the ergastic material? Agave grows in dry sites which receive intense solar irradiation. Does this suggest a potential function????

    Agave Epidermis Lower Surface seen with Bright Field illumination

    Agave Epidermis Lower Surface seen with crossed Polarizers

    Uniseriate (Single Layer) Epidermis:

    This is the most common type of epidermis.

    The following features should be noted:

    Stomata should receive special attention. Sections may reveal Guard Cells cut in more than one plane.

    Note whether guard cells are in the same plane as rest of epidermis, or if they are raised or sunken.

    Subsidiary Cells may or may not be present. The arrangement of subsidiary cells and guard cells can be used to identify plants.

    We will study Pyrus (pear) leaves as an example of a dicot.

    Sugarcane (Saccharum) or ko will be used as an example of a monocot.

    A special feature to note is the prominent bulliform cellsThese are involved in leaf expansion and in the folding of leaves subjected to drought.

    Ancient Hawaiians brought many varieties of ko with them. The stems were sucked or eaten raw. Sugarcane eventually became a major plantation crop in Hawaii but this epoch is coming to an end.

    These images display various aspects of Epidermal anatomy with an emphasis on Stomata.

    Agave Leaf stained with Toluidine Blue: Note the thick Cuticle which has stained light blue

    Unstained Leaf Section: Locate the Guard Cells & decide if this is a Sunken Stomata or not.

    Leaf stained with Toluidine Blue: Locate the Guard Cells & other Epidermal Cells

    What is the position of the guard cells compared to the surface of the leaf? What type of Stomata is this?

    Stomata from the Hawaiian Silver Sword: How would you describe the surface position of these stomata????

    Stomata without Subsidiary Cells

    Two different Stomata with Subsidiary Cells

    Trichomes are treated here in a broad sense to designate unicellular and multicellular appendages that develop from epidermal cells.

    Unicellular Glandular Trichome (Urtica)

    Multicellular Glandular Trichome (Coleus)

    Unicellular, multicellular and glandular hairs can be seen on petioles of Pelargonium (geranium), Passiflora foetida (Passionflower) plus stems & petioles of Pentas & Widelia stems.

    Are these unicellular or multicellular? Are they dead or alive?

    Cross section of ohi'a lehua Leaf: Note the Trichomes (T) and the Cuticle (C)

    Same leaf viewed with crossed Polarizers

    The degree of pubescence for ohi'a lehua is related to altitude and rainfall. The greatest amount of pubescence is observed at high elevations and low rainfall. What are the potential functions of these trichomes?


    Stinging Hairs - Observe commercial slides of Urtica, (Stinging Nettle) leaves. Find the stinging hairs. These work like hypodermic syringes and inject a powerful chemical upon contact.



    Closely related species in Hawaii have hairs that closely resemble their mainland cousins but lack the noxious secretion. This is probably due to the absence of herbivores in these islands. What is the advantage gained by NOT producing the secretion?

    Scales or Peltate Hairs are large complex structures which can resemble umbrellas or shields.

    You may have noticed that kukui leaves are lighter than other leaves in the forest. This is due to the presence of multicellular nonglandular trichomes.

    Kukui Trichomes

    Large, complex Glandular trichomes are known as Colleters. These have multicellular stalks which can contain vascular tissue.

    Plumbago Bud

    Plumbago Flower

    Plumbago Colleter


    What is the most probable source of the red pigment in Sundew Colleters?

    There is a native Drosera (D. anglica)

    Drosera Colleters

    Cotton Fibers:

    Cotton is the most important vegetable fiber and has staged a commercial resurgence recently.

    Hawaiian cotton has been useful in the genetic improvement of commercial cotton cultivars.

    Multiple Epidermis:

    The presence of a multiple epidermis is rare and is restricted to the leaves of certain families like the Moraceae (Breadfruit & Figs) , and to orchid roots. The multiple layers can be traced back to the Protoderm which is the primary meristem for the Epidermis. Thus, two or more cell layers are derived from the protoderm. A good example of multiple epidermis is found in Ficus (Fig) leaves.

    • Make free-hand cross sections of Ficus leaves. Note the many layers of achlorophyllous cells on the upper side of the leaf. These constitute a multiple epidermis. You would need to do a developmental study to be certain about this.

    The epidermis of Ficus is also known for crystals called cystoliths which are found in certain epidermal cells called lithocysts.

    Find these in the Ficus leaf sections and compare with commercial slides.

    Ficus Leaf with a Multiple Epidermis & Lithocyst

    Section of an Orchid root with a Velamen

    Orchid Root: Mature Velamen covers the white area.

    The Velamen of orchid roots is another example of a multiple epidermis. The cells are dead at maturity and can store free water. This is important for epiphytes because their roots may be directly exposed to the atmosphere. There is an Endodermal-like layer between the Velamen and the living parenchyma of the root. This suggests that the root in a manner similar to that which occurs at the Endodermis which separates the cortex from the vascular tissues may take up water.

    Velamen stained with Toluidine Blue

    Velamen seen with crossed polarizers


    Kukui Habitat

    Olive Tree

    Kukui Leaves