In the first part of this series, we mentioned that the edge (also called the margin) of a leaf is useful in helping us identify trees. Then we gave a detailed list of words we can use to describe the margins of a leaf. These words often have Latin etymology, and to prove this, we supplied the Latin source words and their meanings.
Here we will take a similar approach. Since the shape of a leaf is a useful clue in identifying trees, we will provide some words to describe it. These words often have Latin etymology, so just like before, we will supply the Latin source words and their meanings. Below is a list of words describing the shape of a leaf, and their respective etymology.
Also, I encourage you to check out the pictures at Virginia Tech’s dendrology website.
Lanceolate leaves are long and slender, much longer than they are wide. In other words, they have the shape of a lance. This is not surprising, as the English word descends from the Latin word lanceolatus, which means, having the form of a lance. Lanceolate leaves are found on willow trees.
Spatulate leaves have slender bases and very broad tips. This is also not surprising, as the word spatulate comes from the Latin spatula, meaning a broad, flat piece. The Latin word itself comes from the Ancient Greek word, spáthē, meaning any broad blade of wood or metal. Water oak leaves are spatulate.
Heart-shaped (or “cordate”)
The word cordate is used in botany to describe something that is heart shaped. It descends from the Latin word cor, which means heart. In case you are interested, the English word core also shares this etymology. Redbud leaves are cordate.
We call the leaf shape orbicular when the overall shape is circular, rounded, or orb-like. This differentiates it from not only the above shapes, but also from more oblong or elliptical shapes. The word orbicular comes from the Latin word orbis which means circle, ring, or orb. The Romans used the phrase orbis terrarum as a name for the world. Aspen leaves are often orbicular, and some more examples can be found at the Illinois NRES website.
We say that the shape of a leaf is ovate when it is shaped like an egg and broadest near the base. The word descends from the Latin words ovatus, which means egg-shaped, and ovum, which means egg. Zelkova leaves are ovate. Here are some more examples at the NRES site.
The word ellipsis comes from Ancient Greek and means a lack or omission. The same word also exists in Latin. We are all familiar with the typographical ellipsis, indicated by three dots, signifying an omission of words. But how do we get from this sense of the word, omission, to the mathematical shape of an ellipse? The name for the mathematical shape comes from the Greek geometer Apollonius of Perga, who studied conic sections. The cross section which forms a parabola meets the base at an angle equal to the external angle of the cone. For a hyperbola, this angle is greater than the external angle, and for an ellipse, it is less. This is a rushed way of explaining why Apollonius chose these names for the conic sections. Back to the subject, though. Elliptical leaves, like their namesake, are ellipse-shaped and symmetrical. One example are the leaves from spicebush trees. Here are some more examples at the NRES website.
Obovate leaves are like ovate leaves turned upside down. Obovate leaves are egg-shaped, but broadest near the tip. Get the difference? You can understand this visually by comparing the outlines of an ovate leaf and an obovate leaf. The leaves of some magnolia trees are obovate, such as the Magnolia kobus and the Magnolia obovata.
As the NRES explains, oblong leaves are two to four times longer than they are wide. The leaf tip and base can be any shape, and the sides are close to parallel. The word oblong comes from the Latin word oblongus, which means more long than wide, and is itself a compound of the Latin prefix ob- and the adjective longus, which means long. American and Chinese chestnut leaves are oblong.