Spreading the Word
Typical Appearances
Briefing
Prevention
First Aid
Medical Care
Identification
Stems
Stem Identification
Aerial Roots
Black Spots
Phototropism
Apical Dominance
Reproduction
Foliage
Risk Management
Biochemistry
Anecdotes
Bibliography
Appendices
Black Spots
Click photo to view larger image.
Top: A poison-oak stem with black spots. The poison leaks out wherever an injury occurs, and turns black when the air hits it. Two of the leaf stalks also happen to have black spots.
Dr. Guin popularized a Black Spot Test, which you can use to amaze your friends. Youll need three assistants and:
Plastic disposable glove
3 x 5 card
Snack sized Ziploc bag
Quart Ziploc
Scissors
Alcohol pledget
Two plastic grocery bags, one for the trash.
Slip on the glove. Have someone hold the 3 x 5 card. Grasp a poison-oak leaf with your gloved hand, and snip the leaf stalk with the scissors. A drop of clear or milky fluid will form at the cut. That amount, on bare skin, is enough to cause a rash in many people; and its so easy to get that much on you, while out for a walk!
Touch the leaf stalk to middle of the card. Then discard the leaf in the trash bag, held open by a third person. A fourth person tears open the alcohol swab, and presents it to you. You take the pledget with your gloved hand; they throw the packaging in the trash. You swipe the scissor blades with the swab; then throw it in the trash. Secure the scissors. Put the 3 x 5 card in the snack bag, carefully; try not to smear the sap. Put the snack bag inside the quart bag (So far there have been no reactions to double-bagged specimens). Note the time.
In ten minutes the spot on the card will be yellow.
In an hour the spot will be brown.
In 24 hours it will be black.
The stain persists; made 9-6-00, photo 11-29-06
This shirt has been washed fifteen times.
The substance is used in India to mark cloths at laundries.Many problems are caused by poison from horizontal stems that root. Here are some examples:
Photos by Shirley Sparling
