This species presumably has an alternation of heteromorphic generations for which information on the presumably filamentous sporophyte is lacking. Gametophytes are foliose and flaccid, pink, pale reddish to reddish brown in colour and translucent. Blades are characterized by a short stipe; are round, oval, elongate to irregular in shape and 1-12 cm wide by 6-25 cm tall, and are divided along a line in the thallus (zipper) separating the male and female sectors when reproductive (Image A). In section vegetative regions of the blade are monostromatic, 25-58 µm wide, with each cell containing a single stellate plastid with a central pyrenoid (Image B). In surface view cells of vegetative regions of the thallus are characterized by angular to rounded outlines, 10-25 µm in diam. (Image C).
We have 11 genetically verified collections from the Canadian Maritime Provinces to central Labrador, NL, typically from the low intertidal on rock. This appears to be a summer-fall annual based on our records
Note that there are a number of monostromatic foliose bangiophyte species in the Canadian flora (for the NW Atlantic see Mathieson & Dawes 2017), which can be difficult to identify especially in the absence of reproduction. Definitive identification requires molecular data.
Image A. Pressed collection from low intertidal on rock clearly showing the sectoring of blades into female (left) and male (right) sectors (Brier Island, Bay of Fundy, NS: GWS009765).
Image B. Section (rehydrated) through a vegetative portion of the blade (GWS009765).
Image C. Surface view (rehydrated) of a vegetative portion of the blade (GWS009765).