Monographs Details: Thlaspi montanum var. fendleri (A.Gray) P.K.Holmgren
Authority: Holmgren, Patricia K. 1971. A biosystematic study of North America Thlaspi montanum and its allies. Mem. New York Bot. Gard. 21: 1-106.
Family:Brassicaceae
Description:Species Description - Glabrous, mostly glaucous perennials with a simple (mostly) to branched caudex; stems 1-9(-18), slender (about 0.7-2.3 mm thick at tip of upper cauline leaf), (6-)8-22(-28) cm tall (including the mature infructescence), rarely branched, (3-)5.5-13(-22) (averaging 9.6) cm tall below the infructescence, greenish, straw-colored, or purplish; basal leaves numerous, greenish to purplish, oval to oblong, mostly with a denticulate to dentate, sometimes shghtly undulate margin, (8-)22-63(-95) (averaging 40) mm long, (3.5-)6-16(-20) (averaging 10.8) mm wide, the blade (3.5-)9.5-25(-30) mm with a (4-)11-35(-73) mm petiole, the petiole (0.6-)0.9-2.2(-3.3) (averaging 1.4) times as long as the blade; cauline leaves (4-)7-16(-21), sessile (seldom short-petiolate on lower cauhne leaves) and auriculate-clasping, greenish or purphsh, with a very narrow entire to dentate, usually hyaline margin and an obtuse to acute apex, mostly strongly overlapping and extending to the base of the infructescence, (4.5-)9.5-20(-25) (averaging 12.8) mm long, (2-)4.5-12(-17) (averaging 7) mm wide; petals (6-)6.5-11.4(-13) mm long, white to pinkish-purple, spatulate, (1.5-) 2-4.1(-4.9) mm wide; sepals greenish to purplish with a narrow hyaline border, (2.6-)3-4.7(-5.3) mm long; longer stamens (4.2-)4.4-6.2(-7.5) mm long, the shorter ones (3-)3.7-5.5(-6.5) mm; anthers yellow (very rarely purple); infructescence (1-)2-7.5(-11) (averaging 7.5) cm long, (2.5-)3-4(-4.5) cm wide, mostly rather compact; pedicels (5-)8-23(-32) (averaging 15) in lower 2 cm of infructescence; pedicels mostly horizontal to horizontal-descending, the lower ones (3.7-)6-9(-10) mm long, becoming shorter upwards; silicles mostly horizontal to horizontal-ascending, obovate to obcordate, from truncate to emarginate at the apex, mostly winged, greenish to purplish, 7-11.5(-16) (averaging 9) mm long, (4-)4.5-6(-9) (averaging 5.3) mm wide, the length (1.3-) 1.4-2(-2.1) times the width, mostly tapering to a short (1-3 mm) stipitate base; seeds 4-6 per silicle, dark brown, lightly striate, some with a prominent raphe, 1.6-2.1 mm long; style (1.8-)2.5-3.5(-4.2) (averaging 2.9) mm long. Flowering time: March-June (October?). Chromosome number: n = 7.

Discussion:

Thlaspi fendleri Gray, Plantae Wrightianae [Smithsonian Contr. Knowledge 5(6): 14. 1853] 2: 14. 1853.

T. prolixum A. Nelson, Am. Jour. Bot. 32: 287. 1945. (A. & R. Nelson 1822, Arizona, rich clay soil, San Carlos Indian Reservation, about 20 mi W of Rice, near the road to the mesa and canyon country, 9 May 1935, holotype, RM!; isotype, MO!).

T. stipitatum A. Nelson, Am. Jour. Bot. 32: 288. 1945. (.4. & R. Nelson 1196, Arizona, mountains between Ruby and the Tucson-Nogales Highway, Pena Blanca Mts., S of Tucson, not far from Ruby, 15 Mar 1935, holotype, R M I; isotypes, GHI, MO!, NY!, S!, UC!, US-2!, UTC!, WTU!).

Type. New Mexico [on the Organ Mts., N E of El Paso], 1852, Wright 1322 (Lectotype, GH!; isolectotype, GH!, MO!, UC!; lectotype by Wooton & Standley).

Variety fendleri is recognized by a combination of the following characters: a) floral and fruiting parts averaging longer than normal for the species, i.e., styles more than 2.5 mm long; petals 6-13 mm long; silicles 7-16 mm long and 4-9 mm wide; b) plants usually without a branched caudex, and rarely with non-flowering basal leaf rosettes present; c) infructescence mostly rather compact (5-32 pedicels in the lower 2 cm of the infructescence) and with a very short peduncle, if any. Some confusion has existed over the plant which Gray (1853) actually intended to name T. fendleri. In his discussion he considered two different plants, one a cohection by Fendler (44, 1847, C, F, GH-2, MO, NY, S), the other by Wright (1322, 1852, GH-2, MO, UC). Since Gray cited and mainly described the Wright specimen, Wooton and Standley (1915) interpreted it as the type. Payson followed their interpretation, believing that Rydberg had considered the other (Fendler) specimen as the type in view of the fact that he had described T. purpurascens as a new species.

Nelson (1945) described two species, T. stipitatum (Pena Blanca Mts., Arizona) and T. prolixum. (San Carlos Indian Reservation, Arizona), which fall into the range of variation for var fendleri as here recognized. Nelson indicated that the two new species were most closely related to T. fendleri. He considered T. stipitatum to differ in its much larger size, greater leafiness, large oval dentate basal leaves, and stipitate silicles. The type specimens, though described as two separate species, appear to be the flowering and fruiting counterparts of each other. One of the characters used by Nelson for distinguishing T. stipitatum was the stipitate base (1-2 mm) below the fruit. This character is of no taxonomic value within this complex as even the type of T. alpestre var glaucum has fruits with stipitate bases 1-2 mm long.

Perhaps this taxon represents merely the robust end of clinal variation from the small-flowered T. parviflorum. Whereas the latter would seem to have isolated itself by virtue of self-pollination, var fendleri has not. Numerous specimens cannot be separated with any satisfaction from var montanum. Several different patterns of clinal variation exist from north to south in the United States, any one of which could arbitrarily be chosen to represent var fendleri. From this standpoint, it could be argued that var fendleri does not represent a recognizable taxonomic entity. However, the average person cannot help but be impressed by the showiness of the flowers of these plants, and it can be separated by the above combination of characters, which correlates with geographic distribution.

Distribution:United States of America North America|