352 COMPARATIVE MORPHOLOGY OF FUNGI 



imperfect forms which, when the male sexual organs are lacking, can 

 function subsidiarily with the pseudogamous fertilization of the tric- 

 hogyne. The strongest support for this conception would be found if the 

 trichogynes could copulate with ordinary vegetative hyphae. No 

 such case, however, has yet been observed. Just as in the Pezizales, 

 so in the Lichens, this amphimictic sexuality of the Ascobolus carbonarius 

 type is still further withdrawn and replaced by deuterogamy. It appears 

 first that copulation with conidia is no longer complete. Thus, in 

 Anaptychia ciliaris (Baur, 1904) and possibly also in Physcia pulveru- 

 lenta (Darbishire, 1900) there still appears an open communication 

 between conidium (spermatium) and trichogyne tip but no nuclear 

 migration occurs and the trichogyne walls are no longer dissolved ; instead 

 there occurs, at least in the former, a parthenogamy between ascogonial 

 cells, upon which the ascogenous hyphae develop. As in Lachnea 

 stercorea and, under certain conditions of nourishment, in Pyronema 

 confluens, the amphimictic sexual act is introduced but no longer com- 

 pleted and replaced by deuterogamy. 



As a consequence of this emancipation of conidial fertilization, it 

 is well to observe, as in Cudonia lutea of the Geoglossaceae, the trichogynes 

 projecting into the open are formed in species which lack conidia. 

 Whether the trichogynes here are of a rudimentary character and regarded 

 more ontogenetically, will soon disappear or whether they are conserved 

 by a change in function, is at present still uncertain. Lindau (1899) 

 imagined that the trichogynes, which are functionless as sexual organs, 

 assist in the opening of the thallus for the hymenia and in the 

 taking up of oxygen and hence he calls them terebrator hyphae; his 

 interpretation, however, rests upon histologically incorrect conceptions. 



As in the Pezizales, the functionless trichogynes of the Discomyce- 

 tous lichens rapidly degenerate. At first in Parmelia acetabulum (Moreau, 

 1922) and Icmadophila ericetorum (I. aeruginosa) (Nienburg, 1908), as in 

 Cudonia lutea of the Pezizales, they undergo an early degeneration and 

 the sexual acts are then apparently parthenogamous or pseudogamous. 



As in the Pezizales, this functional degeneration then becomes morpho- 

 logical. Thus in Cladonia gracilis (Wolff, 1905), as in Rhizina undulata 

 of the Pezizales, the typical helical form is lost and the ascogonia form 

 only thick, deeply staining, irregularly twisted hyphae. 



In Parmelia tiliacea (Lindau, 1888), Xanthoma parietina (Wolff, 

 1905) and Baeomyces rufus (Sphyridium byssoides) (Nienburg, 1908), as 

 in Spathularia velutipes and Humaria granulata of the Pezizales, tricho- 

 gynes are no longer formed, thus still more effacing the specific character 

 of the ascogonia. 



Finally, as in Baeomyces roseus (Nienburg, 1908), Stereocaulon paschale 

 (Wolff, 1905) and Solorina saccata (Moreau, 1916), like Trichoglossum 

 hirsutum, Humaria rutilans, Pustularia vesiculosa and Aleuria tectoria 



