16. Ray florets 12-15; disc florets 40-75; style apex yellow.
17. Apex of pales truncate with 2 mm long, narrow, apiculate tip; scandent shrub; cymes in oppositely branched panicles on long slender branches;
achenes 3.5 mm long. 11. M. fragrans.
17. Apex of pales gently tapering to a short, broad tip; erect shrubs; cymes in irregularly branched compound dichasia on short thick branches; achenes 2.5-3.0 mm long. 10. M. ovalifolia.
16. Ray florets 6-8; disc florets 90-135; style apex with black spots.
18. Pales with deep apical sinus (2 mm deep at maturity), margins irregular;
achenes 3.5 mm long; upper stems purple, synllorescence a group of irreg- ular cymes with heads tightly clustered on short peduncles; tree. 14. M. josei.
18. Pales without apical sinus, margins entire; achenes 1.0-2.5 mm long; upper stems green; synfiorescence with cymes at ends of long slender branches of oppositely branched panicles; tree or shrub.
19. Shrub; leaves (including petiole) 7-16 cm long, blades ovate-lanceolate to rhombic, unlobed; ligules 6-10 mm long. 12. M. angulala.
19. Tree; leaves (including petiole) 20-90 cm long; blades ovate, often shallowly to deeply lobed; ligules 12.5-13.0 mm long.
13. M. qitadrangularis.
15. Heads pendulous at late an thesis and in fruit; mature pales straw-colored or purple;
plants of Mexico and Central America.
20. Disc florets 85-120, corollas 2-3 mm long; plants of Central America.
21. Leaf-margins usually deeply and irregularly 3-5-lobed, irregularly dentate, abaxial surface densely white-pubescent, petiole with two distal auricles', achenes sculptured, 3 mm long; erect shrubs. 19. M. hibiscifolia.
21. Leaf-margins unlobed to shallowly and regularly 3-lobed, entire to serrate, abaxial surface green, petiole with or without auricles, with or without broad wings; achenes smooth, 2.0-2.5 mm long; shrubs or vines.
22. Petioles sometimes auriculate but otherwise unwinged; apices of disc florets, styles and anthers yellow; ligules of ray florets 12-24 mm long;
disc corollas 2 mm long. 17. M. atriplicifolia.
22. Petioles both auriculate and winged to base; apices of disc florets, styles and anthers with black areas; ray florets 10-12 mm long; disc corollas 2.5-3.0 mm long. 18. M, pteropoda.
20. Disc florets 23-60, corollas 3.5-4.75 mm long; plants of Mexico and Guatemala.
23. Three main veins of leaf branching at base of laminar portion of blade, petiole unwinged and without auricles; mature pales 7.5-10.0 mm long with deep sinus (2 mm deep at spine); disc florets 20-35, 16. M. karwinskii.
23. Three main veins of leaf branching above base of laminar portion of blade, petiole at least partially winged, usually auriculate; mature pales usually over 10 mm long (8-17), apex usually tapering, without sinus or with sinus less than 1 mm deep; disc florets 30-60.
24. Tree; mature pales with apex truncate or sloping, sinus present; ach- enes 3-4 mm long, sculptured; apex of style black; disc corollas green turning yellow. 20. M. hexagona.
24. Shrub; mature pales with apex tapering, sinus absent; achenes 2-3 mm long, surface smooth; apex of style yellow; disc corollas yellow.
15. M. leucantha.
15mm
Fig. 24. Mature fruiting heads of section Montanoa. A, M. tomentosa subsp. tomentosa (Ramos n., OS); B, M. tomentosa subsp. tomentosa (Arsene 268a, US).
IA. Montanoa subgenus Montanoa section Montanoa
Much branched shrubs to 3 meters (rarely small trees); ray florets 0-6 (usually 5), white or cream; disc florets 3-17 (usually 8-9), yellow; pales at anthesis 2-4 mm long; pales at fruiting more or less pentagonal with broad base, 4.5-10.0 mm long, veins inconspicuous, abaxial surface densely glandular and pubescent;
achenes 2.5-3.5 mm long; heads deciduous. Type species: Montanoa tomentosa Cerv. in Llave & Lex. Species 1.
The taxa of this section have a number of features in common. The fruiting head is distinct in having relatively small indurate, densely pubescent, glandular pales with stiff recurved tips (Fig. 24). There is usually only one mature achene per head, although there are up to 17 disc florets. The entire head is deciduous at maturity and is dispersed easily by wind across the hard-packed ground in the dry areas they inhabit. Figure 24 illustrates two heads. They share the following features: xeric or semi-xeric habitat as well as similar involucres, ray and disc florets, and pubescence type. Eighteen species have previously been described in this section and with all of the similarities among the species, the number of characters available to delimit these species is limited.
Of the 18 species described in this section only 13 have been recognized by the
last worker (Blake, 1926a). He listed 11 species from Mexico, had previously
described one from Guatemala (Blake, 1924a), and later described one more from
Mexico (Blake, 1950). In Blake's key as well as his descriptions he relied heavily
on characters such as leaf shape and margin. The same is true of the earlier work
5cm |
Fig. 25. Greenhouse leaf variation in Monianoa tomentosa subsp. tomentosa (FRa 2382, OS): A, leaves from the "dry" greenhouse; B, leaves from the "wet" greenhouse.
by Robinson and Greenman (1899) in which they recognized nine species. When trying to use the keys and descriptions there proved to be so many intermediates that identification was rarely certain.
An examination of flowering and fruiting characters among the 13 previously recognized species resulted in the conclusion that they were essentially identical with the maximum amount of variation occurring in individuals or within the same population. All the collections of this section were then placed together and the leaf morphology was examined to ascertain its usefulness for taxon delimi- tation. The 13 species were broken down into four groups. The first group consists of three previously recognized species from central Mexico. The leaf morphology was examined on the populational (intra- and inter-) and individual levels. The range of leaf morphology found is illustrated in Figs. 9 and 10 (in the
LEAF MORPHOLOGYsection). All the variability found in these species can be seen in the populational sample from the Distrito Federal, Mexico (Fig. 9D). The leaves have several features in common: blades longer than broad, more or less deltoid, with cordate or truncate bases and irregular dentate margins that are rarely deeply lobed. They exhibited a great deal of variation in the greenhouse experiments (Fig. 25). All of the variation found throughout the range of this group can be found on the individual and populational levels (see Figs. 10-12).
The second group includes seven species and ranges from Jalisco, Mexico to Costa Rica. The leaves of these species show a different type of variation from that found in Group 1 but for the same reasons. The interpopulational variation as well as the distribution is illustrated in Fig. 26 (the leaves were selected to maximize the amount of variation). There is a tendency for individuals in Central America to have 3-lobed leaves and for those in Mexico to have 5-lobed ones.
Also, some individuals in San Luis Potosi have acute leaf bases whereas those
in the rest of the range have partially winged petioles. The variation at the
individual level is illustrated in Fig. 27A-C with three individuals from the ex-
tremes of the range. Note the individual from San Luis Potosi has both acute and
partially winged bases. In addition, leaves in both the western and southern
collections have both 3- and 5-lobed leaves (Fig. 27A, C). In the intrapopulational
sample (Fig. 27D) the large irregularly margined leaves were collected from suck-
er snoots. In the greenhouse experiments the leaves from the "dry" greenhouse
(Fig. 28A) were much smaller but retained the same lobed margin as those from
the "wet" greenhouse (Fig. 28B). All the individuals of this group have leaves
that are usually as wide as they are long, are more or less pentagonal, with
partially winged petioles or with acute bases, and their margins are entire with
3-5 lobes.
•• + • V
5 cm
f 4 +
** * 4 *
Fig. 27. Intrapopulational and individual leaf variation in Montanoa tomentosa subsp. xanthii- folia: A-C, Individual variation (Jalisco, AL 3872; San Luis Potosi, FH2207; Costa Rica, FGo 3065);
D, intrapopulational variation (Jalisco, Lake Chapapa).