16 CRUCIFERAE 



6. OXYSTYLIS Torr. & From. 



Annual. Leaves with 3 leaflets, lon<r-petioled. Flowers in liead-like axillary 

 sessile clusters. Petals saffron yellow. Stamens separated from the petals on the 

 elevated and somewhat fleshy receptacle. Ovary borne on a short stout stipe, retro- 

 curA'cd over the receptacle, didymously and unilaterally '2-l(jbed; ovules 2 to each 

 cell. Fruit 2-seeded and didymous, the lobes obovoid, forming closed nutlets with 

 thin soft covering and leaving a circular perforate scar where they separate from 

 the corky thickened axis; style long, subulate, becoming indurated and spinescent. 

 — Species 1. (Greek oxus, sharp, and stulis, column or style.) 



1. 0. lutea Torr. & Frem. Stem stout, erect, usually simple, 1 to 3 feet high, 

 flowering from the base; leaflets oval, % to IVo inches long, on short (1 line long) 

 petiolules; bracts subulate; petals elliptic, 1 line long; nutlets 1 line long; fruiting 

 style spine-like, 3 to 4 lines long. 



Sandy hollows in the hills, 100 to 2000 feet : Death Valley region. Mar.-Apr. 



Gyno-monoecious condition. — Tke following facts have been worked out under our direction 

 by Ethel Crum. "The lower heads are in most cases composed entirely of perfect flowers, the 

 upper of pistillate flowers. On young plants, such as J. T. Eowell 3619 (Bradbury Well, Black 

 Mts.), all flowers seem to be perfect. Mixed heads arc rare but one was found in a collection 

 from the Amargosa Desert (Jones) and one in a collection from Salt Sprs. (Parish 9877). Other 

 heads on these two plants are apparently pistillate. The gyno-monoecious condition seems best 

 developed in very mature plants. 



"Perfect flowers have the stamens much more advanced in development than the pistil which 

 is very small in comparison. The torus is about .25 mm. high, bulbous on one side, the stipitate 

 ovary" inserted on the opposite side of the apex. In pistillate flowers of the same age, or even in 

 unopened buds the pistil appears much better developed, the stipe and style are stouter, the 

 latter more reflexed, and the lobes of the ovary much larger. The apex of the torus is less asym- 

 metrical and the bulbous projection smaller in proportion to the size of the ovary. In some fully 

 matured perfect flowers of lower heads with corolla expanded and stamens well exserted, the pistil 

 appears so minute as to suggest that it never normally develops, so that an imperfectly mon- 

 oecious condition results, the lower heads staminate, the upper pistillate. This view is corrobo- 

 rated by the fact that in plants from Clayton Valley, Nev., Purpus 6421, there remain old pe- 

 dunclesfrom which the flowers have fallen, but which have developed few or no spines and fruits. 

 In cases where a few spines are present they adhere as tenaciously as in the normally fruiting 

 heads. Of course an alternate explanation is that such flowers failed of fertilization." 



Note on the fruit. — The flowering clusters are dense and there is very little expansion of the 

 inflorescence in fruiting. Since the matured branches of the inflorescence, the fruit axes and the 

 spines, are persistent, the fruiting inflorescences are, therefore, much congested, forming, with 

 their spiny styles an involved burr-like body 1^/4 to ly^ inches in diameter. The fruit consists 

 of a pair of pendulous lobes borne strictly on one side of the axis. The lobes mature as nutlets 

 which separate from the fruit axis by a circumscission just below the apex, the circumscission 

 resulting in a small circular opening or scar in the top of the nutlet; there is also formed a similar 

 characteristic scar on the fruit axis. Scattering of the nutlets is gradual, since those on the inside 

 of the "burr", though becoming free by circumscission, are held by the complex rigid axes and 

 spines, and only tardily released. Burs may retain some of the nutlets until the next year after 

 maturity or until freed by weathering. 



Locs. — Furnace Creek Canon and Saratoga Sprs., Funeral Mts. (Contrib. U. S. Nat. Herb. 

 4: 68) ; Amargosa Eiver at Zabriskie and Salt Spr. (Bot. Gaz. 65: 338) ; Bradbury Well, Black 

 Mts., J. T. Eowell 3619. Amargosa Desert, w. Nev., Jones. 



Eefs. — OxYSTYLis LUTEA Torr. & Frem.; Frem. 2d Eep. 313 (1845), type loc. Amargosa 

 River, Fremont; Jepson, Man. 409 (1925). 



CRUCIFERAE. Mustard Family 



Herbs with alternate leaves, no stipules and the flowers in terminal bractless 

 racemes. Sepals and petals each 4, regular and distinct. Petals commonly with 

 claws, the blades spreading in the form of a cross. Nectar glands 4 (or sometimes 

 fused in lateral pairs), papillate. Stamens 6, commonly tetradynamous (4 long 

 and 2 short), sometimes subequal, sometimes 4 or 2. Ovary superior, 2-celled by a 



Jepson, Flora of California, vol. 2, pt. 1, pp. 1-16, Sept. 17, 1936. 



