The Collaborative International Dictionary of English v.0.48:

ascomycetous \ascomycetous\ adj.
   1. of or pertaining to ascomycetes.
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Ascomycetes \As`co*my*ce"tes\, n. pl. [NL.; ascus + Gr. ?, ?,
   fungus.] (Bot.)
   A large class of higher fungi distinguished by septate
   hyph[ae], and by having their spores formed in asci, or spore
   sacs; the sac fungi. It comprises many orders, among which
   are the yeasts, molds, mildews, truffles, morels, etc. The
   class is coextensive with the phylum Ascomycota. --
   As`co*my*ce"tous, a.
   [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

ascomycetous
    adj 1: related to or characteristic of fungi of the class
           Ascomycetes