Notes: According to my reference Collema subnigrescens is quite abundant in my country and is similar to C. nigrescens, which often presents isidia, and to C. ryssoleum, which also lacks isidia; Of the three species is the one with bigger apothecia, in general. Other differences are related with the form and size of the spores:
- C. nigrescens has acicular to baciliform spores, 6 to 11-septate with dimensions: 50-90 x (2.5)3-4.5 um;
- C. ryssoleum has ellipsoidal to fusiform spores, which are wider at center, 5- septate with dimensions:25-45(-50) x (4-)5-8(-10) um;
- C. subnigrescens has acicular spores with one of the ends wider than the other, often curved, 6 to 7-septate with dimensions: (35-)40-75 x (4-)4.5-6.5 um.
I think that the attached photos have sufficient material to lead to the conclusion that this specimen belongs to C. subnigrescens. Concerning the spores I got the following average dimensions: Me = 42 × 5 um ; Qe = 8.4 (N=11), in the ranges: 35.9 – 52.7 x 4.7 – 5.6 um.
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Created: 2014-05-27 16:48:39 PDT (-0700)
Last modified: 2014-05-29 08:39:46 PDT (-0700)
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