Parathecial apparatus

In contrast to the primary structures these are not derived directly from the primordium. They are added secondarily to the primary elements. Some of these are preparathecial sensu lato (Bellemere, 1967) others comprise the parathecial apparatus sensu stricto. 

Pertusaria, and Thelotrema (Letrouit-Galinou, 1966). These types are difficult to interpret. All three cited have in common a secondary preparathecial envelope but lack a parathecial apparatus sensu stricto. Furthermore the primary corpus is reduced because the circumcentral plexus is lacking and the apothecia are more or less perithecioid. 

Buellia canescens (Fig. 32) The primary corpus (A) is derived from a plexiform primordium. It consists of a pericentral envelope, a paraphysogen-ous subhymenial apparatus, and a transitory paraphysoid apparatus. Next, a proparathecium (B), probably homologous to a preparathecial formation, is added to the primary corpus. It has an apical parathecial ring from which is derived the parathecial apparatus sensu stricto. The much reduced primary corpus in Lecanora subfuscata and Lecidea elaeochroma produces the parathecial apparatus directly. 

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