4:8 SURVEY OF THE REPRODUCTIVE PROCESS 



^ 



iew, that a process of this kind is kno\\Ti to occur in the 

 genus Syzycfites, a mould common on decaying agarics.* 



The order of the Lichens may be noticed here on account 

 of their close analogy to the ascophorous Fungi in their 

 organs of fructification. The reproductive organs, known 

 under the name of apothecia, have long been recognised ; 

 they have generally the appearance of shield-like discs of a 

 different colour from the rest of the frond or thallus, and 

 contain sporiferous thecse, intermingled with filiform or 

 clavate processes (abortive thecse), termed poraphyses, both 

 placed in a perpendicular position, and forming the coloured 

 layer of the apothecium. The co-related organs are of later 

 discovery, and are termed spermagonia. They consist of 

 small cavities in the thallus, indicated externally by puncti- 

 form apertures, serving for the emission of the spermatia, 

 which exactly resemble those of Fungi, and are produced 

 like them on the ends of filaments projecting from the walls 

 of the cavities.*!* 



Besides these two forms of fructification many Lichens 

 possess other minute organs, called pycnidia, outwardly 

 resembling spermagonia, but containing corpuscules termed 

 stylospores, which differ from spermatia in being usually 

 oval or pyriform, hollow, and of large size — that is, alto- 

 gether more like spores. In some species (as Scutula and 

 AhrotJialliis) these pycnidia seem to replace the spermagonia, 

 on v/hich account, and from the existence of certain inter- 

 mediate forms, Dr Lindsay is inclined to consider them as 

 modifications of these organs. J But as organs kno-vvn as 

 pycnidia co-exist in certain Lichens with spermagonia of the 

 ordinary character, and in some cases yield corpuscules 



* Griffitli & Henfrey's Micrograph. Diet., p. 626. Berkeley's Crv-pto- 

 gamic Botany, p. 295. 



t Tulasne Comptes Eendus. March 24', 1851. Ann. Nat. Hist. N.S., 

 YIII., 114, XXXII., 427. 



X Quarterly Joum. of Micros. Science (Jany., 1857) p. 53. 



