The effect of water stress on the moss Dicranum polysetum Sw. was studied in the growth chamber, and water potential (ψ) was found to vary as much as 15 atm between the tip of the plant and areas 2 to 4 cm within the cushion, which suggests that very little water is transported from the base of the stem to its tip. With an infrared gas analyzer it was determined that photosynthesis ceases at −21 to −23 atm and the moss remains dormant until it is rewetted. Upon rewetting, there is a sharp burst of respiration that doubles the normal CO2 output. This burst reached its maximum level of 4 mg CO2 g−1 h−1 within 15 min and was of short duration. Full photosynthetic rate was restored in 8 h.

No abstract

One hundred and sixteen species of lichens and 138 species of mosses are reported from the little collected Fort McMurray region of northeastern Alberta. Several significant range extensions are noted. Six lichen species (Chaenotheca chrysocephala, Dermatocarpon moulinsii, Lecanora polytropa, Physcia millegrana, Physconia grisea, and Ramalina pollinaria) and two moss species (Calliergidium pseudostramineum and Hygroamblystegium noterophilum) are new to the flora of Alberta.

Because of nomenclatural confusion, a North American endemic moss species and a distinctly different Eurasian species have both been referred to as Dicranum drummondii C. Mueller. Evidence is presented to indicate that this name should be applied to the Eurasian species and not the North American one as is commonly done. This leaves the North American species without a name. Dicranum ontariense is proposed as the new name and a description and distribution map are given.

No abstract