At the Laguna Rim, at a known location of this species.

This is easily separated from H. rubescens, the only other Heuchera in San Diego County, by its (relatively) wide petals and included stamens. See:

http://tchester.org/plants/analysis/heuchera/heuchera_socal.html

This is a follow-up to an observation by @galash and represents a northern range extension of 350 km for Myriopteris intertexta: https://www.inaturalist.org/observations/39517183

Leaves lanceolate to ovate-deltate, 3-pinnate at base. Pinnae segments round to ovate. Abaxial surface of pinnae segments covered with branched hairs, partly concealed by wider scales. Scales on abaxial surface of costa long lanceolate, deeply cordate at base, with overlapping basal lobes. Rhizome scales bicolored, with broad well-defined dark central stripes and narrow, light brown margins. Spores averaging more than 55 µm in diameter.

More than 100 plants were observed on a basalt cliff with an east aspect. Many of the plants were large and presumably very old. There are many kilometers of similar habitat in the lower Deschutes River valley and its tributaries. With this observation and another recently verified location in the Painted Hills north of Mitchell, it's clear that M. intertexta is well established in north central Oregon. Additional surveying will likely turn up other populations. I would not be at all surprised to find it in similar basalt outcrops in central Washington.

Amidst the one zillion plants in this post-burn area which I and others have called Mentzelia veatchiana, there were two patches of a small number of plants with a much bigger flower, with petals twice the length (and hence four times the area) of the "normal" M. veatchiana.

The two patches of the big-flowered plants were found in quite different areas. The first patch was just over the first saddle when the trail hits a south-facing slope. The second patch was at the bottom of the drainage at mile 1.0, on the bouldery east-facing bank. In both places combined, there were perhaps about 20 plants total of the large-flowered form, both amidst literally thousands or more of M. veatchiana, which was also in nearly every other habitat for literally miles around.

From the much-larger flower, which was fully open 1.5 hours before sunset, at a time when the flowers of M. veatchiana were mostly closing, I was sure these had to be a different species.

These large-flowered plants key to M. ravenii, and there is a voucher from this trail, probably of these exact plants, determined as M. gracilenta in 2013 by Jon Rebman, but changed to M. ravenii after the JM2 key came out, which separated out those two hard-to-separate species on geographic range.

Observations from my infl sample of the large-flowered plant:

bracts entire to 3 lobed with small white area at base.

sepals 5 mm
petals 10 mm, orange/yellow with prominent red base

style 8 mm

fr 10 x 3 mm.

seeds 3 rowed above mid-ovary.

The description for M. ravenii fits these plants perfectly except for some fl bracts being entire, which is an important characteristic distinguishing Mentzelia species. The original paper on this species explicitly says "bracts 3-5 lobed". But since this is a rare species, and probably had few specimens to examine at the time it was described, it would be expected to have some extension to its characteristics.

Something smells a bit fishy to me here, from the following:

• These plants actually fit the description for M. veatchiana quite well. The only difference is the length of the style, 8 mm instead of (3)3.5-6 mm. But I suspect the upper range is just not given correctly. The petal length is given as 4-7(10) mm, and since floral parts generally scale in size together, I bet that voucher with a 10 mm petals also has an 8 mm style, just like this plant.
• Another branch of the JM2 key explicitly distinguishes M. veatchiana and M. ravenii:

36. St generally spreading; desert scrub, Joshua-tree woodland ..... M. ravenii (2)

36' St generally erect; pine/oak woodland, grassland ..... M. veatchiana (3)

My pix of the two plants growing next to each other show identical stem shape characteristics. And, of course, they are growing in exactly the same habitat, desert scrub. In fact, the one zillion plants here of M. veatchiana are all growing in desert scrub.

• The original paper defining M. ravenii gives the following differences from M. veatchiana:

M. ravenii has yellow petals while the desert populations of M. veatchiana are usually deep orange;

M. ravenii has a spreading habit in contrast to the strict pattern of M. veatchiana;

the bracts of M. ravenii are much broader and often clasping, while those of M. veatchiana are narrow and not clasping.

I would call the petals of the large-flowered plant yellow, but the color often depends strongly on lighting.

For the second one, there seems to be no difference in the habit.

For the third one, the difference in the bracts, if any, seems to be the opposite of what was claimed. The bracts of M. ravenii are narrower in my sample, and the bracts of M. veatchiana are also clasping.

• As mentioned earlier, the original paper explicitly says the flower bracts are 3-5 lobed, whereas these plants have at most 3 lobes in the sample I took home, with plenty of entire bracts.

OK, there you have my take on what is going on here. Basically, it is clear that there are two separate size classes of flowers here, accompanied possibly by differences in the flower bracts. But it is not at all clear to me whether this means there are two species here or not.

Independent of the determination of the plants here, whether M. ravenii actually is a separate species is not clear to me either. The original paper, published in 1971, says "[M. ravenii] is rare both in nature and in herbaria". 42 years later, there are only 11 vouchers of M. ravenii in the Consortium, from just 5 different localities.

I do note that the chromosome number is said to be different, 2n=54 for M. veatchiana and 2n=36 for M. gracilenta / M. ravenii, which may or may not argue for making these different species.