Guide to Liverworts of Oregon: Fossombronia longiseta Aust.
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Fossombronia 1b seta long > Fossombronia 2a spore lamella close together > Fossombronia longiseta
Synonym: Fossombronia hispidissima Stephani
Special Status: None.
Recognition: Distinguished from the other two species with long setae (Fossombronia pusilla and Fossombronia wondraczekii) by spore characters given in the keys: this species has high lamellae packed closely together. The spore morphology of this species is quite variable, some having continuous lamellae and some with the lamellae broken up into short segments like spines (hispidissima phenotype). Both phenotypes may occur in the same capsule (Doyle & Stotler 2006). However, both exhibit a similar, distinctive spiny appearance when focused at high magnification on a middle depth of field at margin. This is demonstrated by the stacked photomicrographs below.
Distribution: On soil; most abundant at low elevations in California but not common in Oregon. Often found on road cuts and trail cuts.
Comments: This species has been treated unevenly in the past. Early versions of this Guide to Liverworts of Oregon have Fossombronia longiseta mixed up with both Fossombronia pusilla and Fossombronia wondraczekii based on earlier misapplication of proper name. See their species pages for photo documentation of their current taxonomic placement.
The description of Fossombronia longiseta in Flora of North America provisional treatment (Crandall-Stotler & Bray 2019) emphasizes that it has very long elaters, 280 - 320 µm. The citation includes M. Howe (1899) mentioning this in reference to the original publication by Austin in 1869. This seems to have been entrenched in subsequent literature without adequate documentation of accurate measurements. I have measured all elaters in the images posted here where elaters are clearly identifiable from end to end, using the scale in each image calibrated by a stage micrometer. The results: range 140 - 185 µm. Mean = 165 , n = 6. This matches the general range of elater length measured in the other species of Fossombronia in Oregon and California. Likewise, the elater morphology is relatively consistent: two spirals, rarely three spiral, with little variation in width of the spirals.
Fossombronia sp. Alameda Co., California. DHW s.n. 2 June 2004.
Fossombronia longiseta Horizontal elater = 175 µm. Hastings Reserve, Monterey County, California. DHW m1219
Fossombronia longiseta Horizontal elater = 185 µm. Hastings Reserve, Monterey County, California. DHW m1219
Fossombronia longiseta Upper elater = 161 µm; lower elater = 165 µm. Hastings Reserve, Monterey County, California. DHW m1219
Fossombronia longiseta Elater in left image = 140 µm. Wagontire Rock, Monterey County, California. DHW m1239.
Fossombronia longiseta Elater is 165 µm. Mendocino County, California. Langenheim & Tadros 7 II 1954 (UC 999230)
Fossombronia longiseta/pusilla Wagontire Rock, Monterey County, California. DHW m1235. This is from a mixed collection, all from same patch. L = Fossombronia longiseta. P = Fossombronia pusilla
Fossombronia longiseta/pusilla From Howe (1899), plate 99. Figs. 16, 18 = Fossombronia pusilla. Figs. 17, 19, 20 = Fossombronia longiseta.
Distal aspect. Calif., Fresno Co., east side of Diablo Range, Little Panoche Detention Reservoir. Doyle 8124 (UC).
Proximal aspect. Calif., Fresno Co., east side of Diablo Range, Little Panoche Detention Reservoir. Doyle 8124 (UC).
Lateral aspect. Calif., Fresno Co., east side of Diablo Range, Little Panoche Detention Reservoir. Doyle 8124 (UC).