Discussion

Generic segregations have reduced Gnaphalium from hundreds of species to ca. 38. North American species (north of Mexico) not included here have been segregated to Euchiton, Gamochaeta, Omalotheca, and Pseudognaphalium. Species of Gnaphalium in the strict sense (adopted here) are usually ca. 3–30 cm, loosely tomentose and not glandular, and have loosely glomerulate heads, involucres 2–3(–4) mm diam., white-tipped inner phyllaries, papillate cypselae, and readily falling pappi of distinct bristles, features especially contrasting with Pseudognaphalium, to which most North American species have been transferred. Because of their relatively small stature and tendency to produce loosely spiciform arrays of heads, gnaphaliums sometimes are identified as gamochaetas, which have different cypselar vestitures and different pappi. The lectotype species of Gnaphalium is G. uliginosum Linnaeus; discussion of this choice rather than Pseudognaphalium (Gnaphalium) luteoalbum (Linnaeus) Hilliard & Burtt is given in C. Jeffrey (1979), O. M. Hilliard and B. L. Burtt (1981), and J. McNeill et al. (1987). Gnaphalium polycaulon Persoon is included in the key because it probably will be found in warmer coastal localities in the United States (perhaps Florida or California). It is a cosmopolitan weed (Old World native) and occurs in Mexico. It has sometimes been identified by the misapplied name Gnaphalium indicum Linnaeus.

Discussion

Generic segregations have reduced Gnaphalium from hundreds of species to ca. 38. North American species (north of Mexico) not included here have been segregated to Euchiton, Gamochaeta, Omalotheca, and Pseudognaphalium. Species of Gnaphalium in the strict sense (adopted here) are usually ca. 3–30 cm, loosely tomentose and not glandular, and have loosely glomerulate heads, involucres 2–3(–4) mm diam., white-tipped inner phyllaries, papillate cypselae, and readily falling pappi of distinct bristles, features especially contrasting with Pseudognaphalium, to which most North American species have been transferred. Because of their relatively small stature and tendency to produce loosely spiciform arrays of heads, gnaphaliums sometimes are identified as gamochaetas, which have different cypselar vestitures and different pappi. The lectotype species of Gnaphalium is G. uliginosum Linnaeus; discussion of this choice rather than Pseudognaphalium (Gnaphalium) luteoalbum (Linnaeus) Hilliard & Burtt is given in C. Jeffrey (1979), O. M. Hilliard and B. L. Burtt (1981), and J. McNeill et al. (1987). Gnaphalium polycaulon Persoon is included in the key because it probably will be found in warmer coastal localities in the United States (perhaps Florida or California). It is a cosmopolitan weed (Old World native) and occurs in Mexico. It has sometimes been identified by the misapplied name Gnaphalium indicum Linnaeus.

Discussion

Generic segregations have reduced Gnaphalium from hundreds of species to ca. 38. North American species (north of Mexico) not included here have been segregated to Euchiton, Gamochaeta, Omalotheca, and Pseudognaphalium. Species of Gnaphalium in the strict sense (adopted here) are usually ca. 3–30 cm, loosely tomentose and not glandular, and have loosely glomerulate heads, involucres 2–3(–4) mm diam., white-tipped inner phyllaries, papillate cypselae, and readily falling pappi of distinct bristles, features especially contrasting with Pseudognaphalium, to which most North American species have been transferred. Because of their relatively small stature and tendency to produce loosely spiciform arrays of heads, gnaphaliums sometimes are identified as gamochaetas, which have different cypselar vestitures and different pappi. The lectotype species of Gnaphalium is G. uliginosum Linnaeus; discussion of this choice rather than Pseudognaphalium (Gnaphalium) luteoalbum (Linnaeus) Hilliard & Burtt is given in C. Jeffrey (1979), O. M. Hilliard and B. L. Burtt (1981), and J. McNeill et al. (1987). Gnaphalium polycaulon Persoon is included in the key because it probably will be found in warmer coastal localities in the United States (perhaps Florida or California). It is a cosmopolitan weed (Old World native) and occurs in Mexico. It has sometimes been identified by the misapplied name Gnaphalium indicum Linnaeus.