Excerpts from Jim Conrad's
from the the May 17, 2009 Newsletter, issued from the Siskiyou Mountains west of Grants Pass, Oregon:
If you pay attention to wildflowers in western North America you can't miss the monkeyflowers, by which is meant the genus Mimulus in the Snapdragon Family, the Scrophulariaceae. California's Jepson Manual profiles about 65 Mimulus species for that state, and they're all colorful, attention-getting wildflowers. A few monkeyflower species occur in the East, but nothing like here.
Like snapdragons, monkeyflower blossoms are bilaterally symmetrical and bugle-shaped. The Latin name Mimulus, applied to the genus by Linnaeus in 1753, derives from mimus, which means "buffoon," because of what Linnaeus considered the flowers' clownish bright colors, frequent spotting and irregular shapes.
In the very bottom of a shallow ditch along a road through the valley below us there's one spot about 20 feet long and two feet wide currently resplendently yellow with hundreds of slender, close-packed, yellow-blossomed monkeyflowers. You can see a small part at the top of this page.
Above there's a close-up of a single blossom, noteworthy features of which are: 1) how the floor of the flower's "throat" bulges upward forming a "palate" reducing entry into the corolla's interior; 2) the long, outward-pointing, soft hairs at the throat further restricting entry to small insects, and; 3) the five "pleats" or "wings" running longitudinally along the cylindrical calyx's sides.
If I had to name the plants in the picture I'd say that they're probably MIMULUS GUTTATUS. However, the very similar species Mimulus tilingii also occurs here. Plants in the ditch's moister, deeper soil in the very bottom were most like M. guttatus while those in drier, thinner soil around the edges answered more to M. tilingii. A fine page comparing and illustrating the two species, and remarking that some experts suspect that the two species are just one, is available here.