Plants of Southern California: Cheilanthes clevelandii and C. covillei
Fig. 1. Left: Cheilanthes clevelandii, growing out in the open (the area is mostly in sunlight) with erect gray-green fronds. Right: C. covillei, growing in a shady somewhat-hidden spot (there is only a small sliver of sunlight above the boulder shading the fern) with non-erect bright-green fronds. Both species were growing a short distance away from each other on the PCT north of Warner Springs, photographed on 16 March 2014. Click on the pictures for larger versions.
In the Jepson Manual eflora in 2014, all Cheilanthes species have been moved to Myriopteris; see Grusz and Windham, PhytoKeys 32: 49-64, 2013 for the interesting story behind the resurrection of the Myriopteris name from the year 1852. I retain the Cheilanthes name in this page, since it is much more familiar.
The main intent of this page is to show photographs of the plants and especially the leaves side by side, in Figs. 1 to 3, to show the differences between these two species.
The Jepson Manual and Flora of North America keys are given at the bottom for reference, but they are primarily intended to determine vouchers of an entire plant, including the rhizome, and generally are not very helpful if all you have is a photograph of a plant.
These two species are very similar in that they both have beady segments with papery scales on the back. Normally, it is fairly easy to tell them apart, since C. clevelandii is a larger plant that grows with erect gray-green fronds out in the open, whereas C. covillei is a smaller plant with a mostly non-erect bright green frond that grows in shady somewhat-hidden spots. See Fig. 1 for these typical differences.
While there is often a significant difference in size, there is sizeable overlap in the size of leaves. The Jepson Manual Second edition gives the leaf (including the petiole) of C. clevelandii as being 15-30 (40+) cm, and the leaf of C. covillei as being 8-22 (30+) cm. Hence both species can have leaves 15-22 cm long, and larger leaves are also not unique to one species.
Fig. 2 shows the size and color difference of the leaves from the plants in Fig. 1, with views of both the top and bottom of the leaf in the same photograph. Keir Morse had the brilliant idea to photograph samples of each species side by side, and he is the "hand model" in the photograph.
Fig. 2. C. covillei partial leaf on left (length ~3 cm), and C. clevelandii partial leaf on right (length ~ 7 cm). Click on the picture for a larger version.
Fig. 2. Left: Upper surface of leaves. Right: Bottom surface of leaves. In both pictures, C. covillei is on the left (length of this partial leaf is ~3 cm), and C. clevelandii is on the right (length of this partial leaf is ~ 7 cm). Click on the pictures for larger versions.
Fig. 3 gives a closer look at the leaf segments for both species. The terminal ultimate leaf segment appears to be more elongate for C. clevelandii, at least for this specimen. However, since this characteristic is not mentioned as a difference in the floras, one should be cautious about using this characteristic without further verification that it is a reliable difference.
Fig. 3. Left: Upper surface of leaves. Right: Bottom surface of leaves. In both pictures, C. covillei is on the left and C. clevelandii is on the right. Click on the pictures for larger versions.
The key to separate these two species in the Jepson Manual eflora is not easy to use on pictures. For reference, it is:3. Rhizome scales 1- or 2-colored, dark brown or black, some with narrow light brown margin; scales on abaxial leaf ± > 1 mm wide, obscuring surface, exceeding margin ..... C. covillei
3' Rhizome scales 2-colored, with dark mid-stripe, light margins; scales on abaxial leaf ± < 1 mm wide, not obscuring surface, ± exceeding margin ==> C. clevelandii
The Flora of North America (FNA) key is also difficult to use in photographs. It is:10 (9) Costal scales ciliate on basal lobes only, thus often appearing to lack cilia; ultimate segments glabrous or with a few entire to weakly ciliate scales abaxially, lacking branched hairs; stem scales usually dark brown or black throughout, rarely with narrow, light brown margins. ....C. covillei
+ Costal scales conspicuously ciliate over most of proximal 1/2; ultimate segments pubescent abaxially with branched hairs and ciliate scales; stem scales usually bicolored. ==> C. clevelandii
The FNA also has these helpful comments:Cheilanthes covillei can be difficult to distinguish from the closely related C. intertexta and C. clevelandii; it differs from these two species in having glabrous blades and costal scales ciliate only on the basal lobes. (comment in C. covillei description)
Although some specimens of Cheilanthes clevelandii can be difficult to distinguish from C. covillei and C. intertexta, the species is restricted to the coastal mountains of California and Baja California, and it rarely overlaps the ranges of these closely related species. (comment in C. clevelandii description)
Copyright © 2015 by Tom Chester
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Last update: 13 February 2015