Special Topics #1: Purshia and Fallugia

Special Topics #1

Purshia and Fallugia

Recently I was at the Wild Animal Park where I saw two shrubs that I thought I recognized as apache plume (Fallugia paradoxa) but which were signed as antelope bush. This got me to thinking about the differences between these closely-related genera. Fallugia is a monotypic genus in California with paradoxa as the single species, and Purshia has only two species, mexicana var. stansburyana (recognized in Munz's A California Flora as Cowania mexicana var. stansburiana) and Purshia tridentata which is separated into vars. tridentata (not found south of the Sierras) and glandulosa (extending from Southern California to the eastern Sierra Nevada range), which Munz and Abrams considered as two species.

These illustrations and pictures show the variety in pistils and fruit for these four taxa. Each pistil produces one ovary, and thus one fruit. I don't have pictures that clearly show the pistils in among the many stamens that are typical of the Rosaceae, so the easiest way to count the pistils is to count the number of fruiting structures. The Jepson Manual gives the number of pistils for Purshia tridentata as 1(-3), meaning usually 1 but as many as 3, without differentiating between vars. tridentata and glandulosa. Munz's Flora of Southern California says mostly one pistil for Purshia tridentata var. glandulosa, which is the Southern California variant. Abrams and the older Munz's California Flora say pistils one, rarely two, for the genus Purshia, but 5-10 for Cowania stansburiana, which is now Purshia mexicana var. stansburyana in the Jepson Manual. Note the change in spelling of the species name from older sources. The illustration in Abrams shows two fruits for Purshia tridentata var. glandulosa, and one fruit for Purshia tridentata var. glandulosa, which would seem to imply that this is the typical case, and that is what my photographs appear to show, although this may not always be the case. All sources say numerous pistils for Fallugia or cliff rose, and my pictures show the multiple feathery achenes for that species.

from Abrams Illustrated Flora of Pacific States

2480 formerly called Purshia tridentata now Purshia tridentata var. tridentata
2481 formerly called Purshia glandulosa now Purshia tridentata var. glandulosa

now

2478 Fallugia paradoxa
2479 Purshia mexicana var. stansburyana

Purshia tridentata var. tridentata
Sierras

The following three pictures show what I believe to be var. tridentata. They were taken at an approximate elevation of 7000' on the east slope of the Sierra Nevadas. One of the key discriminants between the two variants is the hairiness of the upper leaf surface, and the third picture appears to show a densely hairy surface. The number of pistils is clearly one per flower which corresponds with Abrams' illustration, and with his genus description of one, rarely two. between

Purshia tridentata var. glandulosa
East Mojave and Short Canyon

The following pictures are of var. glandulosa since that is the only variant in Southern California. They show double fruits indicating two pistils which again corresponds with Abrams' illustration but not with the 'mostly one' description in all sources referred to. One wonders why Abrams chose to illustrate it thusly, and whether these pictures show an atypical population. Unfortunately I don't have a picture which clearly shows the leaf upper surface for this taxon, but the leaves in the third picture in this series do appear to be much more glabrous, although since these were taken in Southern California, there seems little doubt as to the correctness of the identification.

Purshia mexicana var. stansburyana
Cliff rose

I have no pictures from the wild of this taxon, having only seen it at the Rancho Santa Ana and UC Riverside Botanic Gardens. These pictures show the multiple fruits and hence pistils that are typical of this species, and the feathery achenes of the seed head. The Jepson Manual does point out that it hybridizes with Purshia tridentata var. glandulosa.

Fallugia paradoxa
Apache plume

This is another species that I have not yet encountered in the wild, but have seen at the Living Desert, Rancho Santa Ana and UC Riverside Botanic Gardens, and most recently at the native plant garden of the Wild Animal Park in Escondido. According to the Jepson Manual, Purshia comes under generally 1-5 pistils per flower while Fallugia comes under generally 10-many. The second picture shows the typical seed head of apache plume, which is quite different from antelope bush.

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