What Is a Revolute Margin? Leaf Edges Rolled Under
A revolute margin is a leaf edge that rolls downward toward the underside of the leaf. The Manual of Leaf Architecture hosted by Penn State defines revolute as a margin turned down or rolled like a scroll toward the lower surface. NC State Extension lists rosemary leaves as revolute.
The short answer
A revolute margin is a leaf edge rolled downward toward the underside. The Manual of Leaf Architecture defines it as turned down or rolled like a scroll plus defines involute as turned up. NC State Extension describes rosemary leaves as revolute. Turn a mature leaf over plus look along the edge to see the roll.
What does revolute mean?
The Manual of Leaf Architecture defines revolute as turned down or rolled like a scroll. On a leaf the margins curl toward the abaxial surface, which is the underside.
| Term | Meaning | Source |
|---|---|---|
| Revolute | Margins rolled toward the underside | Penn State manual |
| Involute | Margins rolled toward the upper surface | Penn State manual |
| Entire | A smooth edge with no teeth or notches | NC State |
| Entire margin | Smooth, not toothed | Utah State |
Source: Manual of Leaf Architecture, NC State Extension plus Utah State University Extension.
How is revolute different from involute?
The Manual of Leaf Architecture defines involute as a margin turned up or rolled toward the upper surface. Revolute is the reverse, with the margins rolled toward the underside. Judge the direction of the roll from the leaf edge.
Which plants have revolute margins?
NC State Extension describes rosemary leaves as opposite, simple, linear, narrow, entire plus revolute. They are green above plus white tomentose beneath, with short dense hairs on the underside. One leaf can be entire plus revolute at once.
How to: step by step
- Turn a mature leaf over.
- Look along the edge on the underside.
- See if the margin curls toward the lower surface.
- A downward roll means revolute.
- Compare with an upward roll, called involute.
- Check several leaves before naming the margin.
Troubleshooting
Curl runs upward: involute. Check the direction.
Roll hard to spot: small leaves. Use a hand lens.
Edge seems flat on young leaves: new growth. Use mature leaves.
For more on leaves see cannabis leaf anatomy, cannabis nodes and internodes plus companion plants when growing marijuana. Kind Seed Co also stocks cannabis seeds.
Sources
- Manual of Leaf Architecture, Cornell University Press, hosted by Penn State
- Extension Gardener Handbook, chapter 3: botany, NC State Extension
- Salvia rosmarinus (rosemary), NC State Extension Gardener Plant Toolbox
- Tree and botanical glossary, Utah State University Extension Forestry
FAQ
Is revolute the opposite of involute?
Yes. The Manual of Leaf Architecture defines revolute as rolled in the abaxial direction toward the underside plus involute as rolled in the adaxial direction toward the upper side. The manual lists the two terms side by side. Look at the edge of the leaf to see which way the margin rolls.
Why do botanists describe leaf margins?
NC State Extension notes the shapes of leaf blades plus margins are useful in identifying species plus cultivars of plants. A rolled edge is easy to spot once you know to look for it. Pair the margin term with the blade shape plus leaf arrangement to narrow down a plant.
Can a revolute leaf have an entire margin?
Yes. NC State Extension describes rosemary leaves as both entire plus revolute. Entire describes a smooth edge with no teeth or notches, while revolute describes the downward roll. One term covers the outline of the edge plus the other covers how it curls, so the two can apply together.
How do I check for a revolute margin?
Turn a mature leaf over plus look along the edge on the underside. A margin that curls down toward the lower surface is revolute. The Manual of Leaf Architecture notes an upward roll toward the upper surface is involute instead. A hand lens helps on small or narrow leaves such as rosemary.
Does rosemary have revolute leaves?
Yes. NC State Extension describes rosemary leaves as opposite, simple, linear plus revolute. They are green above, white tomentose beneath plus less than an inch long. Short, dense hairs grow on the underside of the leaf, so the rolled edge frames a pale strip down the lower surface.
