Ignatov, M.S., E.A. Ignatova, V.E. Fedosov, O.V. Ivanov, E.I. Ivanova, M.A. Kolesnikova, S.V. Polevova, U.N. Spirina & T.V. Voronkova. Andreaeobryum macrosporum (Andreaeobryopsida) in Russia, with
additional data on its morphology
Arctoa (2016) 25: 1–51
doi: 10.15298/arctoa.25.01
Andreaeobryum macrosporum
is
newly found in Yakutia, in the Sette-Daban
Mountain Range, ca. 3000 km west of its known localities in Alaska. This is the
first record of the genus and the class Andreaeobryopsida
outside of North America. The species was found on calcareous rock outcrops,
above the tree line in the Pinus pumila altitudinal belt. The morphology of the Siberian
plants is described, focusing particularly on characters less studied in
previous observations. Among these are: (1) axillary
hairs with a complicated beak structure, apparently regulating mucilage
exudation; (2) anacrogyny and the ability to
substitute half of a leaf with an archegonium; (3)
specific and relatively long sporophyte development
within the epigonium, which is filled with mucilage
mixed with macerated cells from the inner wall of the epigonium;
(4) foot formed by cells with numerous chloroplasts, with inflated surface
cells, sometimes forming finger-like protrusions and with the labyrinth ingrowth in 1–3 layers of the foot surface cells and also
labyrinth structures on the surface cell wall facing placental space, whereas
gametophyte cells have no ingrowth; (5) lobate archesporial tissue, not
fully overarching the columella, which has membranaceous connectives between its segments and reaches
the poorly differentiated outer spore sac, being thus similar to Andreaea in many respects; (6) flattened
seta, which is not due to drying but lacking radial symmetry from the outset;
(7) spore walls lacking or almost lacking an exine. It
seems that Andreaeobryum plant
possesses an ability to concentrate light, as the physiologically important
parts of the structure, the haustorial part of the
foot, the urn base, the archegoniophores and the meristematic zones near leaf bases, look considerably
brighter in comparison with other parts of the plant.