D. POPULATION BIOLOGY 



The populations are relatively small, with estimated numbers 

 from around 50 to less than 500 plants. At the site along 

 Muddy Creek, plants occurred both inside and outside of the 

 exclosure. In July, plants were mostly in fruit, with a few 

 flowers . 



E. MANAGEMENT CONSIDERATIONS 



The species is uncommon and occurs in small populations in the 

 study area. These are in habitats that are often heavily 

 grazed. The degree to which livestock impact these populations 

 is not known, but the location of plants both inside and 

 outside the exclosure provides an opportunity to study this. 

 Designation as a sensitive plant by BLM may be warranted at 

 this time. 



Thlaspi parviflorum A. Nels. 

 Small-flowered pennycress 



A. DESCRIPTION 



! . General description: A small glabrous herbaceous 

 perennial in the Brassicaceae (mustard family). The basal 

 leaves have petioles while the stem leaves are clasping, 

 without petioles. The flowers are borne on pedicels and 

 consist of four green sepals, four white petals, six stamens, 

 and a single pistil. The fruit is a silicle which is 

 flattened at right angles to the septum and has a very short 

 style . 



2. Technical species description (adapted from Hitchcock et 

 al. 1964): 



Glabrous perennial with a simple to freely branched 

 caudex, the 1-many stems simple, or occasionally branched 

 above, 3-25 (40) cm. tall; basal leaves usually many and 

 rosulate, 1.5-4 (6) cm long, narrowly oblanceolate to 

 broadly obovate or ovate, entire to few-toothed, narrowed 

 rather abruptly to a slender petiole one-half to twice as 

 long as the blade; cauline leaves usually several, 

 lanceolate to oblong-elliptic, 5-35 mm long, sessile and 

 auriculate; pedicels slender, spreading to ascending, 

 4010 mm long; sepals 1-1.5 mm long, not saccate at base; 

 petals white, 2.5-3 (4) mm long; silicles from more or 

 less elliptic and acute at the apex, to cuneate (truncate 

 at tip) or retuse and more nearly oblong-obcordate, 4-10 

 (13) mm long, the margins keeled and usually slightly 

 indistinctly striate longitudinally (and concentrically) , 

 but apparently smooth except as viewed under a very 

 strong lens. 



