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Acer platanoides leaf

Today, I collected a leaf from a distinctive purple tree near the Franklin Dining Commons. The Norway maple (Acer platanoides) is a common ornamental tree that is often planted in cities because it is hardier and more tolerant of air pollution than native Sugar maples. It has two color varieties: the purple pigmented one and an unpigmented variety that's easy to confuse with Sugar maples. If you're trying to tell them apart, the bark is different on a Norway maple (a criss-cross diamond pattern) and Norway maples have a milky white sap.

Acer platanoides leafAcer platanoides leaf

Figure 1. Acer platanoides leaf. Upper side of leaf is on left.

The leaf is very dark green—almost black, in artificial light. The veins and stem are a reddish purple, especially on the underside of the leaf.

The leaf is palmately lobed with two small lobes near the base and 5 major lobes toward the tip. I had noticed yesterday that the stem of the Horse-chestnut seemed comparatively long, but this stem is much longer relative to the leaf. The stem is half-again longer than the leaf. I noticed, however, that there was a lot of variability in stem length.

The leaf has 11 holes where presumably insects have been consuming leaf material. Most holes run along a vein. One hole spans a vein in the leaf leaving just a narrow bridge across the hole. A number of holes have a kidney shaped pattern with smooth outward borders and a ragged inner border, perhaps related to the pattern of consuming the leaf.

On the underside of the leaf is a small, white cocoon. The area is covered over with a dense layer of white silk.The silk pulls the leaf together to make a small, bent section, where the pupa is concealed.