Samstag, 22. Dezember 2012

Plants of the Day (December 22nd, 2012) - Tortula ruralis (Hedw.) Gaertn., Meyer, & Scherb. & Grimmia pulvinata Hedw. & Sn.

Today's “Plants of the day” aren't a real plants but a mosses. I'm speaking of Tortula ruralis (Hedw.) Gaertn., Meyer, & Scherb from the Pottiaceae family and Grimmia pulvinata Hedw. & Sn. from the Grimmiaceae. In German, T. muralis is known as “Dach-Drehzahnmoos” and in English as “star moss”. G. pulvinata is known as “Polster-Kissenmoos” in German and in English as “gray-cushioned grimmia”.

Grimmia pulvinata Hedw. & Sn.

G. pulvinata belongs to the Bryophyta, so it's a classic moss and no hornwort or liverwort. The Gametophyte grows in round, blue-green to dark-green (moist) or gray (dry) cushions, which are between 1 or 2 millimeters high.

G. pulvinata - habitus; you can see the silver hairs as
white fluff in the periphery. also on this picture are young
Sporophytes with the bent seta (centre)

The narrow leaflets are between 2 and 3 millimeters long and arranged in an spiral leaf-pattern. They have a distinctive leaf-vein on their back and short, silver-gray hair at the tip, which is almost as long as the leaf-blade. In the dry state, the leaflets lie flat on the stem and unfold when become wet.

G. pulvinata - here, you see older sporophytes (brown); 
the seta has erected.

The Sporophyte has a short seta, which is about 3 to 5 millimeters long, so it protrudes beyond the Gametophyte. However, the young seta is bent and erects only when ripening. During this process, the colour also change from a bright green to a darker brown. The oval capsule have a long beak. Young capsules are bright-green but become brown during ripening.

G. pulvinata - on a bollard in the city

G. pulvinata is a very common moss and can be found in cities on walls, gravestones and roofs. It's also very endurable and has no problem with dryness. Sometimes, it can also be found at the bark of trees but never on the ground.

Tortula ruralis (Hedw.) Gaertn., Meyer, & Scherb.

T. ruralis also belongs to the Bryophyta and is a classic moss (no liverwort or hornwort). The golden-green Gametophyte grows in loose turfs, which have an average height between 2 and 4 centimeters.

T. ruralis - habitus

The narrow leaflets are about 5 millimeters long and are curved what gives the whole foliage a star-shaped look (this is also the reason for the name “Star moss”). Their blunt tips also have long, silver-gray hairs, which are about 1 millimeter long (such hairs at the tip are very common at Bryophyta and protects the leaflets against sun-radiation). In the dry state, the leaflets become twisted.

T. ruralis - here, you can see the sta-shaped foliage

The seta of the sporophyte has a red color. The brown capsules are cylindrical to egg-shaped and sometimes a little bit bent. In contrast to G. pulvinata, the seta of T. ruralis is erected right from the beginning. Another interesting feature of the sporophyte are the left handed teeth of the peristome (the rim at the end of the capsule).

T. ruralis - on a wall

The natural habitat of T. ruralis are calcareous rocks but it has become also very common in cities. So, it can be found on walls, gravestones and sidewalks. Next to G. pulvinata, Tortula muralis Hedw. and Hypnum cupressiforme Hedw., it is one of the most common mosses in our cities.

At first glance, T. rutalis looks very similar to Tortula muralis Hedw. from the same genus and a confusion is possible. The main differences between these two species are the seta, which is much longer at T. muralis, and the star shaped foliage of T. ruralis. Another difference is the serrated silver-hair of T. ruralis but this is only visible with a microscope.

Pleas note: in some literature, T. ruralis is called Syntrichia ruralis (Hedw.) F.Weber & D.Mohr

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