Posts Tagged ‘Oemleria’

Mysteries of Cotyledon Leaves

Over the last year or two, I’ve found a new challenge to amuse myself—learning to identify plants by their cotyledon leaves. Dicots get their name from the two cotyledon leaves that emerge from a newly germinated seed. This first pair of leaves often, if not usually, bears no resemblance to the regular leaves found later on the plant. Most likely, the form of these leaves is defined more by the shape or some other characteristic of the seed. Typically, they are more or less oval. Sometimes they have distinct petioles, sometimes they are sessile. One would be hard pressed to identify these unless they were growing in quantity under the mother plant. Some plants, however, have very unusual cotyledon leaves. These really pique my curiosity.

Lotus micranthus

The compound true leaves of two tiny Lotus micranthus solve the puzzle of the red-striped cotyledons

Oemleria cerasiformis?

Might these waterlily-like cotyledons belong to Oemleria cerasiformis? Note also the tiny Nemophila parviflora with its cotyledon leaves still attached.

A couple of years ago, while out on Heckletooth Mountain just east of Oakridge in the fall, some little cotyledon leaves caught my eye. While the shape of the leaf was fairly generic, each one had a distinct red stripe starting at the base and going halfway up the leaf. What could they be? There were plenty of them, and I surmised they were one of many common annuals growing on this low elevation mountain. I brought one home and put it in a pot, hoping to find my answer in the spring. Naturally, I forgot about it over the winter. The following spring, however, there it was again on Tire Mountain, this time with the first true leaf appearing. It was Lotus micranthus, a little annual member of the clover family that is abundant on many of the lower elevation mountains in the area. What a surprise! I checked my pot when I got home, and sure enough, there was a tiny Lotus micranthus. Since then I’ve seen it several times with both the red-striped cotyledon leaves and the first tiny compound true leaves. The stems are red, so perhaps this has something to do with the unusual red stripe on the cotyledons. Read the rest of this entry »

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