Another conspicuous and unfamiliar species observed on glades during the initial canoe expedition was a leafy-stemmed, opposite-leaved herbaceous plant, clearly still some weeks from flowering, whose stem and leaves were so densely beset  with gland-tipped hairs that they gave it a sticky feel. Its overall look was suggestive of a Silphium, but consultation of readily available literature (e.g., Perry 1937, Cronquist 1980)  gave no indication that any taxon so copiously glandular occurred in that genus. In a few weeks the plants began to flower and both their generic placement (Silphium) and their distinctiveness were manifest.

Silphium glutinosum J. Allison, sp. nov. TYPE: Alabama: Bibb County, ca. 17.8 km NE of Centreville, ca. 2 km NNW of the mouth of Alligator Creek. "Alligator Glade," Ketona Dolomite outcrop ca. 0.2 km W of Alligator Creek, 19 Aug 2000, James R. Allison 12503 (holotype, GH; isotypes: AUA, DUKE, FLAS, FSU, GA, IBE, JSU, MICH, MO, NCU, NY, TAMU, UARK, UNA, US, USCH, VDB). Figures 11 and 12.

Species a congeneris combinatione capitulorum radiis vulgo tredecim cum indumento denso pro parte maxima glandulifero caulium et foliorum et involucrorum haud aegre distinguitur.

Perennial herb, fleshy-rooted from a short rhizome or nearly erect caudex, vegetative portion densely pubescent throughout with a mixture of  long, stipitate-glandular hairs and mostly shorter, pointed, eglandular hairs, somewhat resinous-aromatic. Stems 1-several, (3.6) 8-15 (18) dm tall, unbranched except for inflorescence, (4) 5.5-10 (11) mm thick at base, finely sulcate, terete, yellowish green or sometimes maroon-tinted, especially near the base, nodes with persistent leaves at anthesis (4) 6 or 7 (10) below the branching of the inflorescence. Leaves opposite or rarely alternate, very rarely 3 at a node, dull, upper surface dark yellowish green, lower surface paler, margins ciliate; the lowest (at anthesis) the largest, ovate or lanceolate, larger blades 15-22 (24) cm long, 7-12 cm wide, coarsely and shallowly toothed, particularly toward the base, with winged petioles 6-15 (16) cm long, pubescent and ciliate like the blade (often  proximally with longer, eglandular hairs); leaves upwardly gradually reduced in size, with shorter and more broadly winged petioles, becoming sessile and entire and grading into ovate or lanceolate (-broadly elliptic) bracts in the inflorescence. Inflorescence of (1) several to many (>30) heads in an open, broad (to 36 cm) panicle, the branches stiffish, the central peduncle of a main branch 6-13 (15) cm long (laterals shorter), straight (or curved early in anthesis and the heads nodding), bracteolate at the base or sometimes above the middle; involucre shallowly campanulate, 3-4.3 cm⁽⁷⁾ broad, the phyllaries in about 4 series, mostly 19-23, 11-19 mm long and 5.5-11 mm wide, membranaceous, rather loosely overlapping, ribbed proximally, the outermost usually the longest, ascending or sometimes (especially those of the larger, central head of an inflorescence-branch), spreading and with margins and tips somewhat recurving, pubescent and ciliate like the leaves, lanceolate and acute, inwardly progressively reduced and passing through ovate to elliptic and  obtuse and then oblanceolate with a broadly rounded apex, the innermost ca. 8 mm X 2 mm, the pubescence progressively more confined to the distal, dilated portion and the ribbed proximal area becoming proportionately greater;  pales 9-11 mm long, linear-oblanceolate, apices distinctly obtuse, with both glandular and eglandular, scalelike pubescence; rays (8) 12-14 (16), usually 13, (1.7) 2.0-2.7 cm long, linear-elliptic, shallowly emarginate, pale yellow; disk mostly 1.4-2.2 cm broad, the numerous (>60) corollas tubular, greenish yellow, 6-7 mm long, with ascending, broadly triangular lobes. Fruit a broadly ovate to orbicular achene, 6-8.5 mm long (excluding pappus teeth), with wing ca. 1.5 mm wide at the base of the sinus, the body appressed white-hairy and ciliate in  the sinus, otherwise smooth or sparsely pale-strigillose, gray-brown when ripe. Pappus of two teeth 0.5-2.0 (3) mm long, rarely one or two smaller, narrower secondary awns persisting. Chromosome number 2n = 14 (A. and S. 8107, UNA).

Flowering June-October, fruiting July-frost.

English Name: Sticky Rosinweed.

Paratypes. Alabama: Bibb Co., 10.0 km NNE of Centreville, rocky bank of Little Schultz Cr., 15 Aug 1998, J. Allison and M. Moffett  11326 (AUA); 12.1 km NNE of Centreville, "Lady-tresses Glade South," 22 Aug 1999, A. 12170 (AUA, GH, NY, UNA, US); 13.5 km NE of Centreville, Six Mile Cr., "The Sinks," 15 Aug 1998, J. Allison and M. Moffett 11324 (GA); 14.4 km NE of Centreville, "Beaver Glade," 11 Oct 1992, A. and S. 7308 (UNA); 14.6 km NE of Centreville, "Goat Glade South," 8 Oct 2000, A. 12564 (AUA, GA, GH, JSU, UNA, US, VDB); 14.9 km NE of Centreville, "Brown's Dam North Glade West," 16 Aug 1998, A. 11329 (GA, GH, IBE, JSU, MICH, MO, NCU, NY, TAMU, UNA, US, VDB); 15.3 km NE of Centreville, "Desmond's Glade," 22 Jul 2000, A. 12445 (AUA, DUKE, FLAS, FSU, GA, GH, IBE, JSU, MICH, MO, NY, TAMU, TENN, UARK, UNA, US, USCH, VDB).

In contrast with the other Ketona Glade endemics, Silphium glutinosum seems most vigorous in partial shade, though it will grow in full sun of the open glade. Perhaps it is no coincidence that it is also the only endemic taxon of the Ketona Dolomite glades that does not appear to be completely restricted to them. Besides on glades it can sometimes be found in rocky places along streams and occasionally along logging roads in the glade region. In view of this, it is somewhat surprising that it is absent from several glades occurring near the eastern and western extremities of the Ketona Formation in Bibb County.

Both the gradually reduced leaves, and heads usually with 13 rays⁽⁸⁾ align this taxon with the Silphium asteriscus complex (e.g., S. asteriscus L., S. trifoliatum L. and their varieties). Like most Silphium species, S. glutinosum will sometimes hybridize with related species⁽⁹⁾ when they grow nearby. The most common Silphium of roadsides and thin woods in the vicinity of the Ketona Glades is S. trifoliatum L. var. latifolium Gray. Where the glade-forest ecotone had been disturbed by logging or road construction, plants of apparently intermediate morphology were sometimes found (e.g., A. and S. 7301, UNA; A. and S. 7869, VDB). Such plants were also found in rocky areas along major streams of the Ridge and Valley in Bibb County, and were often more abundant than either parental species (e.g., A. and S. 8022, JSU).

Commonly, Silphium trifoliatum var. latifolium is essentially glabrous, but Bibb County populations,  otherwise seemingly typical of the variety, usually have some spreading, transparent, hairs on the peduncles. The presence of such hairs on the putative hybrids, intermixed with shorter, glandular hairs, in combination with intermediacy of leaf shape, petiole length, and involucre morphology, seems proof that such plants are indeed of hybrid origin.

Another, much less common putative hybrid, we observed where the parental taxa grew in close proximity, was Silphium asteriscus L. var. asteriscus X S. glutinosum (e.g., A. and S. 8474, UNA; A. and S. 8475, VDB). As many as three genomes seem to have been involved in the formation of one plant seen along Little Schultz Creek, apparently S. asteriscus L. var. angustatum Gray X S. trifoliatum var. latifolium X S. glutinosum. Other putative hybrids of Silphium but not involving S. glutinosum were also seen, such as S. compositum Michx. X S. laciniatum L. (A. 12508, UNA). As all published chromosome counts in Silphium are diploid (Settle and Fisher 1970, Cronquist 1980, subsequent volumes of Index to Plant Chromosome Numbers), and given the frequency of hybridization in human-perturbed habitats, it appears that, among related taxa of Silphium, barriers to gene flow are chiefly ecological. Alteration of the landscape by humans appears to have disrupted these barriers, just as in Coreopsis.

Of course, taxa with overlapping periods of anthesis but different habitat preferences came into contact occasionally prior to widespread habitat manipulation by humans. It appears that under certain conditions, resulting hybrids may have outcompeted the parental species and founded populations that, over time, became stabilized in their morphology and appear now as fully independent taxa. One possible such taxon, of Tennessee and Kentucky, has been called Silphium integrifolium Michx. var. gattingeri Perry. Kral (1983) opined that these plants suggested a blending of S. integrifolium and S. trifoliatum var. latifolium. Upon examining specimens at VDB the rightness of Kral's interpretation seemed compelling, the large heads with many rays suggesting S. integrifolium, the petiolate lower leaves and smooth stems suggesting in turn S. trifoliatum var. latifolium. The lack of intermediacy in pubescence could be explained by the loss of integrifolium alleles in recombination, or recessiveness of integrifolium pubescence alleles. A hybrid origin for taxon gattingeri has not yet been proven, but support for this hypothesis is provided by a seemingly analogous situation in Alabama.

After showing Robert Kral Silphium glutinosum in the field in Bibb County, he called our attention to densely glandular specimens labeled S. integrifolium he had collected from the Black Belt province of Alabama, in Dallas County (Kral 48820, VDB) and Perry County (Kral 47891, VDB). The authors visited  both of these populations, and "windshield surveying" along highways and back roads resulted in the discovery of well over a dozen additional populations of a densely glandular Silphium in those two counties. After comparison of living populations and preserved material of these plants with S. integrifolium and with S. glutinosum, we determined that a suite of characters exists that distinguish the Dallas and Perry County plant from either of those species. 

The number of ray flowers consistently greater than 13 would cause these plants to key to Silphium integrifolium in, for example, Cronquist (1980), supporting Kral's determinations of his Dallas and Perry County collections. Plants truly conforming to that species, however, are known in Alabama only from two counties (Pickens and Sumter) on the Mississippi border, localities at least 80 km to the northwest of the glandular Dallas and Perry County populations.

Silphium integrifolium differs from S. glutinosum in many respects. The former is, under favorable conditions in the wild and in the garden (e.g., garden of Allison), a taller plant with nodes slightly closer together and therefore more numerous. Those leaves that persist until anthesis in S. integrifolium are normally sessile and, like the stem, eglandular. It also has a narrower inflorescence, on average with fewer but larger heads, these with consistently more numerous rays and phyllaries and with acute receptacular bracts (pales or chaff). The characters of lower leaf petiole length, plant height, and node number are evident in the field but not in the herbarium, as tall species such as S. integrifolium are virtually always represented there only by the inflorescence and a very few upper nodes ("top snatched"); the specimen shown in Settle and Fisher (1970) is typical in this regard.

Plants of the Dallas and Perry County Silphium are intermediate between S. glutinosum and S. integrifolium for some characters and for others resemble one or the other of those species (Table 2). It would be less than satisfactory to treat them as S. glutinosum X S. integrifolium, when they are allopatric with respect to both of those species and therefore have a present existence and future evolution independent of both, not to mention that the Dallas-Perry entity is only hypothetically of hybrid origin. To choose the alternative of making it a new variety (or subspecies) would require selecting one or the other putative parental species as being of closer affinity, when there is, at least at present, no clear basis for choosing between them. As these populations are consistent in their morphology, are readily distinguished from all previously described taxa, and are sympatric with neither of the species they most closely resemble, they are described here as a new species, Silphium perplexum.

Silphium perplexum J. Allison, sp. nov. TYPE: Alabama: Dallas County, ca. 15.5 km SW of Selma and ca. 2.4 km WSW of Old Cahaba; S side Co. Rd. 2 at jct. Co. Rd. 9; prairielike openings over chalk, abundant, 18 Aug 1999, James R. Allison 12153 (holotype, GH; isotypes: AUA, DUKE, FLAS, FSU, GA, JSU, MICH, MO, NY, UNA, US, VDB). Figure 12.

A S. glutinoso J. Allison caule et foliis et involucris glanduliferis accedit, sed radiis semper plus numerosis (plus quam 16) et caule pilis glandiferis brevioribus, et petiolis plerumque brevioribus recedit.

Similar to Silphium glutinosum in having glandular hairs on the stem, leaves, involucres, and pales, but allopatric and growing over chalk rather than dolomite or limestone, differing morphologically as follows: stems averaging taller, mostly 15-20 (24.4) dm, to 13 mm thick at base; nodes usually more numerous, (7) 9 -12 (17); glandular hairs of herbage averaging distinctly shorter, about equal in length to the accompanying pointed hairs. Leaves more often lanceolate and upwardly more gradually reduced, larger blades as much as 30 cm long and 15 cm wide, petioles averaging shorter, at anthesis the longest at most 5-8 (10) cm long. Heads usually a little larger, involucre to 4.6 cm broad, the phyllaries more numerous, mostly 19-32 (35), 8-16 mm long, slightly more chartaceous, the outermost slightly shorter than the next interior, rays more numerous, (17) 19-23 (33), and a deeper yellow; pales with obtuse or acutish apices. Chromosome number: 2n = 14 (A. and S. 8119, GH, UNA).

Flowering July-October, fruiting August-frost.

English Name: Old Cahaba Rosinweed.

Paratypes. Alabama: Dallas Co., just N of Old Cahaba, chalk hills, 6 Oct 1972, R. Kral 48820 (VDB); 19.8 km WNW of Selma, Co. Rd. 45, 14 Jul 1999, J. Allison and A. Schotz 12080 (NY); 20.3 km WNW of Selma, Co. Rd. 88, 18 Aug 1999, A. 12155 (AUA, GH, JSU, NY, UNA, US). Perry Co., dry roadside thickets near Marion, 1 Sep 1885, J. D. Smith s.n. (GH); S of Marion, Ala. Hwy. 5, just N of Washington Cr., prairie remnant, 29 Jul 1972, R. Kral 47891 (VDB); 11.9 km SSE of Marion, Co. Rd. 12, 19 Aug 1999, A. 12161 (AUA, GA, GH, JSU, UNA); 13.4 km SSW of Marion, Co. Rd. 15, 8 Oct 2000, A. 12583 (AUA, GA, GH, JSU, MICH, MO, NY, UNA, US, VDB); 14.5 km SE of Marion, Co. Rd. 6, 19 Aug 1999, A. 12160 (GH, UNA, USCH).

All of the known Silphium perplexum populations are within 13.5 km of the Cahaba River. The type locality is only about 1.3 km from that river, and about 76 km south of and downstream from a riverside population of the Bibb County endemic, S. glutinosum (of course, with meanders the actual length of river is considerably greater). It is easy to envision propagules of the latter being transported downstream by flood waters at a time when the range of S. integrifolium extended somewhat eastward of its present known extent, facilitating hybridization between two formerly allopatric species. The fact that S. perplexum extends over a greater geographic area than one of its putative ancestors, S. glutinosum (ca. 32.4 km across vs. 11.5 km), argues against its formation in the immediate past. In any event, it is certain that its formation preceded 1885 (see paratypes).

One factor that appears to have favored Silphium perplexum over many competing species is unpalatability to cattle. Where prairie habitats within its range have been subjected to grazing—and this would appear to be most, if not all of them—S. perplexum becomes very abundant, sometimes virtually the only plant standing.

As with Silphium glutinosum, we observed putative hybrids between S. perplexum and other species, especially in roadside populations. By far the most common hybrid was Silphium asteriscus var. asteriscus X S. perplexum (Dallas Co.: A. and S. 8580, VDB; A. and S. 8570, JSU, NY; A. 12156 UNA; Perry Co: A. and S. 8564, AUA, US).