Shrubs Of The Great Basin: A Natural History

Spiny Greasebush

Spiny Greasebush ForseUesia nevaaensis THE SPINY GREASEBUSH is almost never a very conspicuous or dominant shrub in the Great Basin. Generally, it occurs in relatively small numbers on steep hillsides or in ravines, mixed with other shrubs such as rabbitbrush, green ephedra, and bitterbrush. It appears to prefer limestone areas, though this is not always the case-one notable stand near Virginia City, Nevada, is located on soils derived only from igneous rocks. In its leafless condition, the spiny greasebush somewhat resembles a rather dark and stiffly angled green ephedra. However, closer inspection will show that many of the smaller branches end in spines, and this is never the case with green ephedra. In the spring, the younger branches of the spiny greasebush produce small, oblong leaves from 5 millimeters to I centimeter long. The tiny, in~ conspicuous, white flowers, with five petals, are produced in April or May and are followed by capsules only 2 to 5 millimeters long, each bearing one or two seeds. During most of the year, leaves are not present; photosynthesis is carried on by the green, angular branches. Characteristically, spiny grease~ bush is only 30 to 60 centimeters tall. If it has any value as a forage plant, this has not been noted. Despite its lack of abundance in anyone area, the spiny greasebush has a wide distribution, ranging from southwestern California north to the drier eastern portions of Oregon and Washington and east through Nevada to Arizona, Utah, New Mexico, Oklahoma, and Texas. The Great Basin spiny greasebush was first described by the famous nineteenth~century American botanist Asa Gray, from material collected in northern Washoe County, Nevada. He described it under another genus name, however, calling it Glossopetalon nevaaense. The genus name honors James Henry Forselles, a Swedish mining engi~ 204 206 CELASTRACEAE neer and botanist of the nineteenth century. The alternate name, Glos, sopetalon, comes from the Greek and means tongue and petal, in reference to the shape of the petals. Lyman Benson and Robert Darrow, in their re, cent book, The Trees and Shrubs of the Southwestern Deserts, consider the Great Basin spiny greasebush to be only a variety of Glossopetalon spinescens; they use the variety name aridum, which refers to this shrub's dry habitat. The genus Forsellesia, which contains eight species, ranges from Washing, ton south to eastern California, east to Idaho, Nevada, Utah, and Colo, rado, and southeast through Arizona and New Mexico to Oklahoma and Texas. Asa Gray thought that greasebush belonged to the bittersweet family, known botanically as the Celastraceae. This family-widespread in the temperate and tropical areas of the world-includes such plants as the burn' ing bush or euonymus, some exotic species of which are commonly culti, vated, as well as Oregon boxwood, Utah mortonia, and the bittersweet of the eastern states. One Middle Eastern tree belonging to this family is the source of Arabian tea, though not the tea of the Orient. There is, incidentally, not total agreement that the spiny greasebush be' longs to the bittersweet family. It may really belong to another family, the Crossomataceae, otherwise known as the crabapple bush family. This family, which presently contains only three genera, is restricted to the deserts of southern Nevada, California, and Arizona. It appears to be distantly related to the magnolias. There are several reasons why botanists have been uncertain on this issue. For one, detailed anatomical, biochemical, and physiological studies which might help decide the relationships of the spiny greasebush have not yet been made. But another and much more fundamental problem when dealing with plants such as this, which have relatively simple flowers, is that so many parts have been lost in the course of evolution that we frequently have to make what amounts to a shrewd guess regarding their possible an' cestors. Several lines of evidence indicate that the earliest flowering plants of about 130 million years ago had many floral parts-many sepals, many stamens, many petals, etc.-and that their flowers were relatively un' differentiated. This pattern would be very much like that of the present,day magnolias. Evolution in the flowering plants, then, to a great extent, has involved the reduction or even the loss of various parts and the increasing specialization of those floral structures that remain. ...