XANTHISMA PSEUDORESTIFORME (ASTERACEAE: ASTEREAE),
A NEW GYPSOPHILE FROM NUEVO LEON, MEXICO

Billie L. Turner
Plant Resources Center
The University of Texas

Austin, TX 78712

ABSTRACT

A new g\psophilK ti oil \ nifhisii.a pseudorestiforme B.L. Turner, sp. nov., is described
from Nuevo Leon, Mexico. It is closely related to the well-known gypsophile X. restiforme from the
area of Cuatro Cienegas in central Coahuila, hence the name. A photograph of the type is provided,

along with photos of the habitat, plants in vivo, and a map showing the distribution of each species.
KEY WORDS: Asteraceae, Xanthisma, gypsum, Mexico, Nuevo Leon, Coahuila

Some 30 years ago 1 described a most remarkable species, Machaeranthera restiformis B.L.
Turner — now identified as Xanthisma restiforme (B.L. Turner) Hartman & Morgan — from gypsum
soils near Cuatro Cienegas, Mexico (Turner 1973), one of the highlights of my many years of
fieldwork in Mexico. The novelty was named for its rope-like stems, nothing else in the genus having
such an appearance, until the following:

Xanthisma pseudorestiforme B.L. Turner, sp. nov. Figs. 1-5. TYPE: MEXICO. Nuevo Leon.
Mpio. Mina, N of Molina, gypsum hillside, 854 m, 26.02219° N, 100.422211° W, shrub 20 cm,

widely scattered plants, 4 Sep 2005, Hinton et al. 28398 (holotype: TEX).

Xanthismi restiformi (B.L. Turner) Hartman & Morgan similis sed differ! caulibus ac foliis
dense hispidulis (vs. gossypinis), capitulis minoribus (4-5 mm in altitudine vs. 6-8 mm), et bracteis
involucralibus setas albas apicales carentibus.

Suffruticose or subshrubs, intricately branched and densely hispidulous, 30 cm tall or less
from a tough, woody taproot, presumably forming deep rhizomes. Leaves simple, short, ovate blades
2-4 mm long, 2-3 nun wide, sessile, densely hipidulous, ciliate with white waxy trichomes that
terminate ill-defined serrations and the apex. Heads solitary, discoid, sessile or nearly so.
Involucres campanulate, the bracts 2-5 mm long in 3-5 series, distinct white apical setaceous
apiculae absent. Receptacles ca 5 mm across, alveolate, adorned with small scales and short hairs.
Florets yellow, 30-60 pel' head; corollas ca 4 mm Song, 5~iobed, the lobes acute, ca 1 mm long. Style
branches flat with densely pubescent, acute appendages. Aehenes prismatic, ca 1.8 mm long,
densely white-pubescent; pappus of numerous stiff bristles ca 4 mm long.

Additional collection-, examined MEXICO. Nuevo Leon. Mpio. Mina: NE of Carricitos,
gypsum hillside, 935 m, 26.0136° N, 100.46592° W, 23 Jul 2007, Hmton et al. 28633 (TEX); off
Monterrey-Monclova Hwy 53, 6 mi N of Rancho Las Estacas on one of several roads leading N from
headquarters — this road passes two watering holes and ends 7 mi N of headquarters, near second
water hole on gypsum, 650 m, 26° 25' N, 100° 50' W, 18 Oct 1993, Patterson 7436 (TEX).

The new species resembles Xanthisma restiforme (B.L. Turner) Hartman & Morgan but
differs in its densely hispidulous steins and leaves (\^ cotton^ -pubeseeu f ). snniLi heads (4-5 mm
high vs 6-8 mm), and involucral bracts without apical white bristles. The novelty indeed resembles
X. restiforme so much in habit so that I have coined its name after the fact. No doubt the two taxa are

Turner: Xanthisma pseudorestiforme, new gypsophile f

derived from some ancient gypseous rhizomatous population, this giving rise to the two remarkable
populations known today — one in Coahuila, the other in Nuevo Leon (Fig. 1). The locality for X.
pseudorestiforme also is the home of two other recently described gypsophilous endemics, Erigeron
heleniae Nesom (Nesom 2007) and Cryptantha geohintonii B.L. Turner (Turner 2008).

Xanthisma pseudorestiforme first came to my attention in 1993 by a collection of Thomas F.
Patterson (cited above). I annotated it as a possible new species at the time, hoping that additional
specimens might be obtained by others, and such has been provided by my good friend George
Hinton, who obtained two more collections, including the type and a color photograph of the same.
In his covering letter (email), George commented:

On Sunday I went to a gypsum outcrop near Monterrey; and as I got out of the truck saw a real
nice Asteraceae, a dominant species. I thought that if no one had been collecting on that
gypsum (most likely) it would surely be undescribed. Then yesterday night I went to the PR.C
website [Plant Resources Center, TEX] and found that you had collected it on gypsum near
Cuatro Cienegas — over 100 miles to the NW of the Nuevo Leon site and 30 years earlier!

George's intuition was correct, of course, but his web site examination could not have picked
up the differences that distinguish between the species concerned, nor did he know that I had
squirreled away the single sheet of the potential novelty at my disposal, as noted above.

ACKNOWLEDGEMENTS

I am grateful to Guy Nesom for the Latin diagnosis and comments on the paper and to Tom
Wendt for the photograph of the holotype. Many thanks to George Hinton for his interesting letter,
some of this quoted above, and the excellent collections and photos.

LITERATURE CITED

Nesom, G.L. 2007. A new gypsophilous species of Erigeron (Asteraceae: Astereae) from

northeastern Mexico. J. Bot. Res. Inst. Texas 1: 891-894.
Turner, B.L. 1973. Machaer anther a restiformis (Asteraceae), a bizarre new gypsophile from

northcentral Mexico. Amer. J. Bot. 60: 836-838.
Turner, B.L. 2008. Cryptantha geohintonii (Boraginaceae), a newly described gypsophile from

Nuevo Leon, Mexico. Phytologia 90: 406^09.

Turner; Xanthisma pseucbrestiforrne, new gypsophile from Mexico 3

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Figure 1 . Distribution of Xanthisma restiforme olldX pseudorestifor

Turner: Xanthisma pseudorestiforme, new gypsophile from Mexico 4

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Figure 2. Xanthisma pseudorestiforme (holotype, TEX).

Turner: Xanthisma pseudorestiforme, new gypsophile from Mexico 5

Figure 4. Xanthisma pseudorestiforme. Branches and head.

Turner: Xanthisma

si gypsophile from Mexico 5

Figure 5. Xanthisma pseudorestiforme. Scattered shrubs at type locality