Flora of North America species comparison

In North America, Grimmia trichophylla is principally a lowland species, occurring in the mountains up to about 1000 m., rarely higher. In the Southern Hemisphere, it may be found up to 4000 m. In New Zealand, the species is common, and in contrast to G. trichophylla in North America, frequently bears capsules. The New Zealand plants are usually smaller than American specimens, and the leaves are frequently contorted. The nearly cosmopolitan G. trichophylla has many phenotypes, and numerous subspecies and varieties have been described. In damp and shaded habitats, the awns may be short, just as in dry unfavorable habitats at high altitudes, where stunted specimens may occur with small, short leaves and reduced awns, or even with muticous leaves. Grimmia trichophylla has frequently been confused with related species such as 36. G. muehlenbeckii and 34. G. lisae (see discussions thereunder for identification details). Robust forms of G. trichophylla have been mistaken for G. austrofunalis (H. C. Greven 1997, 2003), which does not occur in North America. Although some of those plants have leaves of equal length along the stem, characteristic of G. austrofunalis, they also have both leaf margins recurved, and the medial and outer basal laminal cells are longer and more robust than in that species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Grimmia arizonae is endemic to the American Southwest and northern Mexico. It has a highly restricted distribution in North America, being found in mountainous areas in southeastern Arizona to the Rocky Mountain Front Ranges of western Texas, New Mexico, and Colorado. It has disjunct sites in western Oklahoma and central California.

Grimmia arizonae is part of a group that includes G. longirostris and G. pilifera. Its sheathing leaf bases, dioicous sexuality and immersed capsules will separate it from G. longirostris. The separation of G. arizonae from G. pilifera, however, has often proven problematic. Grimmia pilifera has been described as having strongly keeled leaves and margins 2–3-stratose, thicker than the medial lamina. (e.g., H. A. Crum 1994c). H. C. Greven (1999) added usually with short-awned, ovate-lanceolate leaves. Grimmia arizonae has less keeled leaves and margins 2-stratose, not thicker than lamina. Greven noted its usually long awns and broadly lanceolate leaves. J. Muñoz (1999), however, synonymized these species, attributing any differences to geographical variations and sexual development. He reported that in eastern North America, and in shade, G. pilifera has long, acuminate apices and distinct ovate bases. In the West, and in sun, its leaves are lanceolate and without distinct bases. We would call these specimens G. arizonae. To Muñoz, the presence or absence of a central strand, is “too variable to be reliable;” he reported that fertile stems have a distinct strand, sterile stems have none. In contrast, in the present study, Hastings found the stem central strand reliable to separate these species. There is no correlation between sexual maturity and strand development; specimens of G. pilifera lack a central strand. Further, the stem epidermis is consistently twice as thick as it is in G. arizonae. Hastings found western specimens, in full sun, that lack a central strand typical of eastern specimens named G. pilifera. Many sterile specimens from Arizona have a central strand, but sterile or fertile, specimens in eastern North America do not have one. Based on these observations, G. arizonae and G. pilifera are not synonymous. Grimmia arizonae differs from G. pilifera by having a central strand, a thin epidermis, and 2-stratose distal lamina with 2-stratose not-thickened margins.

(Discussion copyrighted by Flora of North America; reprinted with permission.)