Asci (from Albert Schneider's A text-book of general lichenology)
Depending on the species, an ascus may contain anywhere from one spore to well over a hundred. This page shows the extremes in the leftmost and rightmost drawings. Most commonly there are eight spores per ascus, as shown in the middle pair of drawings. Often the eight spores are in a row (as in drawing 2), in which case they are described as uniseriate. By contrast the spores in 3 are biseriate, being arranged in two rows within the ascus. Alongside the asci you can see a number of paraphyses, sterile hyphae found amongst the asci in the fungal fruiting body.
1. Umbilicaria pustulata; 2. Leptogium tremelloides; 3. Parmelia perlata; 4. a species in the genus Acarospora.
Note: not all to the same scale
Albert Schneider's A text-book of general lichenology, published in Binghamton in 1897 by Willard N. Clute & Co. illustrates the structural features of various lichens from the north-eastern United States.