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Laticifers are some of the most peculiar elements of the plant body and are found in a restricted number of famous or infamous families and genera. Their infamy stems from the poisonous or addictive nature of their contents. However, the soothing qualities of the latex from the opium poppy led to the development of powerful pain killers like morphine which have made life and death more tolerable for seriously afflicted patients.
Laticifers are long cells or vessel-like series of cells permeating various tissues of the plant. They contain variously colored, often milky juice called latex.
Gallery of Familiar Plants which have Laticifers.
I have grouped these according to Families. I am not concerned that you learn these families or these plants by name. I want you to recognize plants that you see on campus and elsewhere in Hawaii. If you develop an interest in these plants you will want to learn about them for your own fulfillment.
Apocyanaceae
 Cascabela thevetia |
 Cerbera manghas Note the latex oozing from the X cut into the fruit. |
 Stemmadenia littoralis |
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 Plumeria obtusa |
 Nerium oleander |
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Asclepiadaceae
 Hoya bicarinata |
 Calotropis gigantea |
Euphorbiaceae
 Aleurites moluccana kukui
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 Jatropha integerrima
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Moraceae
 Ficus religiosa |
 Artocrpus altis (Bread Fruit)
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Papaveraceae
 Argemone glauca |
 Papaver orientale Oriental Poppy |
Examine Latex production from different specimens. Latex flow may be copious at first but may be absent in many specimens. Latex generally flows from the slender flowering stem of Euphorbia splendens long after it is collected.
Make Longitudinal sections of stems and petioles containing laticifers.
Stain
these with IKI or Sudan.
Laticifers in Breadfruit stain with Toluidine Blue.
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Laticifers stained with IKI |
Laticifers stained with Sudan |
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 Cross Sections of a Young Breadfruit Stem stained with Toluidine Blue |
 Long Section of Breadfruit Stem showing Laticifers stained with Toluidine Blue: Note the BRANCHING!!!!! |
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 Cross Sections of a Young Breadfruit Stem stained with Toluidine Blue |
 High Magnification of Laticifers from the Young Stem of Breadfruit: Note the Starch Grains in the Laticifer on the left. |
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Laticifers in olona (Touchardia
latifoliolata): 
This plant produces incredibly strong "fibers" which were used by ancient Hawaiians to fashion their capes and helmets.
Olona also produced the finest rope for sailing vessels and was unparalleled for its strength and durability until the introduction of synthetic polymers.
These "fibers" are actually laticifers with incredibly thick walls.
Make transverse and longitudinal sections of Mature stems.
View unstained and look for latex.
Examine them with your polarizers.
Stain with Toluidine Blue.
Are the "fibers/laticifers" lignified?
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| Low Mag. View of Olona Stem seen with Polarized Light: Where are the thick-walled cells? | Unstained Laticifers at High Mag: Note the orange Latex in one laticifer, and the thick, translucent walls |
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Longitudinal section of Olona stem viewed with crossed polarizers: What does the birefringence tell you about these cells? |
Olona Laticifers stained with Toluidine Blue |
NECTARIES
Floral Nectaries
These
occur in a wide variety of locations on the flower. Some are easy to detect while others
are not. We will consider only a few here. 
Dissect
the following to find the Nectar and
the structures that produce it.
Then examine available prepared slides.
Bauhinia purpurea
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The Nectariferous tissue lines the opening of
the tubular cavity in the Receptacle.
The Receptacle is that part of the stem 
that bears the flower parts. In this case
it is a long tube.
Most
of the nectar is secreted from an area that is opposite the largest inner vascular bundle. See C in the image on the right.
Locate the Nectariferous tissue and vascular bundle first in fresh material
then look at the prepared slides.
The transverse sections of the receptacle show:
Only phloem occurs in the smallest bundles arranged in an area around the opening.
Phloem
ends in densely cytoplasmic cells.
Larger, more vacuolate cells subtend the epidermis.
The Epidermis and some other cells have yellow, granular contents.
The Epidermis near the largest bundle has stomata but no cuticle.
The Nectariferous cells are the dense, small cells in the lower end of the floral tube wall, just above the ovary.
Carefully
cut cross-sectional chunks off
the tube, starting at the top, to see how 
much of the tube (of an upright flower)
is filled with nectar.
Acerola or Malphigia
Locate the floral nectaries with a dissecting scope.
Are they Floral or Extrafloral?
Ring Nectaries
Many flowers have a "disk" or ring nectary around the base of the gynoecium, e.g., species of Asystasia, Alamanda, Convolvulus and Cucumis
Examine the prepared slide of a median longitudinal section of Cucumis and find the nectary.
Can
you deduce where the nectar is secreted?
Does the epidermis have a cuticle in this region?
Are both xylem and phloem present in the Nectariferous tissue?
Locate similar nectaries on the living flowers.
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 Allamanda sp. |
 Argyreia nervosa (Convolvulaceae) |
Abutilon
The
floral nectaries of various species from this genus and family (Malvaceae) have
been studied more than those of most plants. 
They are located on the upper surface of the base of the Sepals.
The secretory apparatus consists of closely packed Trichomes and subtending tissues in the Sepals.
Obtain
a flower & Peel back Sepals
under a Dissecting scope.
You should see a change in the appearance of the surface near the union of the Sepals and the Receptacle. You may also see some nectar.
Remove some of the innermost Sepal and mount it on a slide with the face UP.
Carefully apply a cover slip and use the Weboski Method to view the Secretory Trichomes. They look like a stack of beads.
Look also at a prepared slide and locate the Secretory Trichomes.
Optional or Demonstration
To see nectar secretion in action, cut a thin transverse section of a sepal through this region and mount in immersion oil.
Look for small droplets of nectar at the tips of the hairs, and watch them grow.
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Extrafloral Nectaries
These usually occur somewhere on leaves, but may be located on stems or bracts.
Ricinus communis (Castor Oil Plant)
Find the two large nectaries on the petiole of a fresh leaf.
Observe a prepared slide that shows the densely stained Nectariferous tissue.
Locate the tracheary elements and determine how close they come to the epidermis. Can you find sieve elements? Do they come closer to the epidermis? Note how the (secretory) epidermal cells are much denser than the two cell layers just underneath. Note also the thick cuticle covering the epidermal cells.
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Ricinus communis |
Extrafloral Nectaries of Ricinus communis |
 Kukui Leaf (look near the base of the blade (lamina) |
Norantea Its floral bracts are modified into large orange tubes that secrete nectar.
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Norantea Inflorescence: The large Orange-Red structures are vase-like Nectaries & the Flower Buds are the small red spherical structures. |
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Passiflora |
Impatiens petioles have nectaries. Impatiens also has a floral nectary. Can you find it? |
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