Observation 80905: Stereocaulon Hoffm.
When: 2011-10-28
No herbarium specimen

Notes: On gravel

I tried to get a closeup on the branches, but I can’t decide if they are tomentose or not..

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By: Jason Hollinger (jason)
2011-10-31 14:09:23 CDT (-0500)

Those might be useful resources for understanding the range of boreal and arctic lichens. Both links worked fine. (The language barrier wasn’t entirely successful at preventing me from using the one site… :)

By: Irene Andersson (irenea)
2011-10-31 06:18:38 CDT (-0500)

I was too lazy to search through this herbarium database (it contains specimen from all the world), let’s see if the link works here:

I looked at another database where people just report their obses (a lot missing there, of course): "http://www.artportalen.se/plants/default.asp
Unfortunately, there is no english version in search mode..

By: Jason Hollinger (jason)
2011-10-31 03:41:50 CDT (-0500)

I think I was getting your two observations confused!

I should be very interested in seeing photos of dactylophyllum. It’s something we should have over here, too, but I’ve never (knowingly) seen it.

Where are you looking for Swedish observations? Is there an on-line database of herbarium records up there?

Thanks again, Jason
By: Irene Andersson (irenea)
2011-10-31 03:08:56 CDT (-0500)

I’ll keep your information in mind, if/when I find more Stereocaulon (we’re planning to spend some time in the alpine area next autumn). Since this is not paschale, finding Nostoc won’t take me further to a 100% ID, but it certainly helps to learn what I see in the microscope..

I have looked through swedish obses of this genus. I found 13 different species reported, and the ones that are lookalikes, all grow in different environments, only tomentosum explicitly in gravel.
Like you said, all dactylophyllum have been found on rocks – and is the most frequent among the reported ones. It’s not necessarily the most common one, I guess it depends on where people have been looking for them.
The second most reported, is paschale. Maybe because it’s one of the easiest to ID when it has special features that rules out all the others.

By: Jason Hollinger (jason)
2011-10-30 14:33:36 CDT (-0500)

Stereocaulon contains two photobionts. All contain primarily Trebouxia, which are indeed just green blobs ~10-15 µm in diameter. Internal structure should be apparent even at 400×. (Trebouxia is a green alga, and therefore a eukaryote with nucleus, chloroplasts, etc.)

The cephalodia contain a cyanobacteria. Nostoc appears as single small uniformly green cells ~5-8 µm wide, or as short chains. Trebouxia never forms chains, Nostoc often does, but sometimes it can be hard to find them.

Stigonema, on the other hand, forms “filaments composed of several rows of cells (multiseriate), filaments up to 1 mm wide; with true branching forming from cell divisions in different planes, cells mostly blue-green in color, oblong to ellipsoid, 9-15 × 3-11 µm.” (from pg. 44-45 of vol. I of Sonoran Flora)

For completeness, their description of Nostoc is: “filaments forming chains of globose to barrel-shaped cells (3-7 µm in diameter) interspersed with larger colorless cells (heterocysts); filaments looking like a chain of beads (”pearl necklace"); chains not branched, widely dispersed… or tangled in compact gelatinous coils."

It sounds like Stigonema filaments should be readily visible under a hand lens. Here’s a (lousy) micrograph I took a few years ago:

I found
By: Irene Andersson (irenea)
2011-10-30 05:11:50 CDT (-0500)

a 30x loupe in a drawer, and managed to see the tomentum clearly now :-)

If I can locate the cephalodia, should I expect to find green Nostoc chains?
What I have found so far in the microscope, are just green blobs..

By: Jason Hollinger (jason)
2011-10-29 17:08:57 CDT (-0500)

With 30 species in Scandanavia alone, heaven alone knows! All I know is I was taught by Trevor Goward that the key to paschale is the “pompom-like cephalodia”. I’m not sure if that’s unique to paschale, or whether it’s the only one in that “group” that has that character. According to Ernie Brodo in Lichens of North America:

S. paschale has more granular phyllocladia [than S. tomentosum], and the cephalodia, which are fibrous and conspicuous, contain Stigonema [instead of Nostoc].

The cephalodia of S. tomentosum are “granular, very dark blue-green, buried in [the tomentum].”

Interesting old article
By: Irene Andersson (irenea)
2011-10-29 15:48:49 CDT (-0500)

among others, dealing with paschale vs tomentosum
Gosh, it’s over a 100 years old..
It argues that it’s not mainly the tomentum that tells them apart, more the apothecia – mainly terminate in paschale, lateral in tomentosum.
Hmm, how many species in between and around them have been discovered since then?
I can understand why this genus is difficult..

Collecting Stereocaulon
By: Irene Andersson (irenea)
2011-10-29 06:39:54 CDT (-0500)

is a very nice idea. About 30 species are supposed to occur in Scandinavia, and over 80 Cladonia species.. Would be a challenge just to find and try to identify a few more of those. And there are lots of rocks to investigate :-)

Far from “terrible”, I’d say
By: Jason Hollinger (jason)
2011-10-28 17:33:24 CDT (-0500)

I’ve never heard of apothecia shape being important on Stereocaulon, but that’s hardly definitive! You could check S. alpinum and S. grande, too. P test could potentially help a bit, too, if you happened to have access to PPD (= paraphenylenediamine).

I think the best suggestion I could give you would be to collect a number of specimens from various habitats and see if you can spot differences. The differences in phyllocladia are very subtle, and they are extremely variable. Maybe if you could build up a good set of reference material you might be able to gain some confidence? You’re in an ideal location, I think, for studying the genus.

Note, by the way, S. dactylophyllum is supposed to grow on rock. Gravel may not qualify, believe it or not. The ones that grow on rock seem not to be able to handle disruption. Animals walking around will disturb gravel regularly. I don’t have a good feel for this, though. It’s the first choice in most keys (growing firmly attached to rock or not, that is), but I’ve never developed any confidence in answering it!

S. tomentosum
By: Irene Andersson (irenea)
2011-10-28 15:16:38 CDT (-0500)

looked to me like the best match, that’s what I was thinking too. I can’t find anything similar except dactylophyllum, but the shape of the apothecia seems different..?
I’m terrible with all lichens, so much new words to learn and details to look at.

Tomentum is usually very obvious
By: Jason Hollinger (jason)
2011-10-28 13:34:07 CDT (-0500)

But I think this one is anyway. Look at the white tufts seen in silhouette. This has the look and feel of S. tomentosum, a very common species in British Columbia. Did I mention that I’m terrible with this genus??

Created: 2011-10-28 08:55:23 CDT (-0500)
Last modified: 2011-10-28 15:17:02 CDT (-0500)
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