Ochrolechia gowardii

The thallus, or body, of Ochrolechia gowardii is very thin and membranous, with a yellowish-white colour. It is partially embedded in the bark (endophloedal) and features scattered, irregularly shaped soralia—structures that produce powdery asexual reproductive granules (soredia). These soralia break through the thallus, creating ragged margins, and measure between 0.5 and 1.0 mm in diameter. The soredia themselves are coarsely granular and yellowish-white in colour. Unlike some other lichens, O. gowardii has a distinct margin but lacks a prothallus, a preliminary growth feature that some lichens exhibit. The apothecia (fruiting bodies) of O. gowardii are commonly present and are sessile, meaning they sit directly on the thallus without a stalk. They are small, ranging from 0.6 to 1.0 mm in diameter, but can occasionally reach up to 1.5 mm. The discs of the apothecia are pale yellow-orange to yellowish-pink or light orange and are usually coated with a coarse, powdery substance (pruina), especially when young. The margins of the apothecia are smooth and even, and they remain level with the disc in mature specimens.

The internal structure of the apothecia reveals a hymenium (the spore-producing layer) that is 230–250 μm tall. …

This lichen is typically found in subalpine forests, growing on the bark of Abies lasiocarpa (subalpine fir) at elevations between 1,300 and 1,650 m (4,270 and 5,410 ft). Ochrolechia gowardii has been recorded in several locations within the northern Rocky Mountains, including British Columbia and Alberta in Canada, and parts of Idaho and Montana in the United States. The known northernly extent of its North American distribution was extended when it was reported from Alaska. It has also been recorded in Sør-Trøndelag and Nordland in Norway, Central Norway, and in the province of Jämtland in Sweden; in both countries the lichen was found growing on Picea abies.

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