THA LL OPHYTES. 



the rupture of its apex. This expulsion is probably caused by the lateral pressure of 

 the swollen paraphyses and the property of swelling possessed by the membrane of the 

 ascus itself. 



The germination of the spores of Lichens takes place by the endospore of each 

 spore-cell putting out a filament which ramifies and creeps upon the damp substratum 

 on which the spore is placed. The origin of the first gonidia has never been observed 

 after the dissemination of the spores ; but Tulasne sometimes found groups of gonidia at 



Fig. 193 —Vertical section of a small portion of the apotheciuin of A^iaptychia ciliaris (x 550) ; m the medullary layer of 

 the thallus; y the hypothecium, together with the sub-hymenial layer; / the paraphyses of the liymenium, tlieir upper ends 

 of a brown colour ; among them are the asci in various stages of development ; in i are the young spores not yet septate, in 

 2-4 the spores more fully developed ; the protoplasm in which the spores are imbedded is contracted by the drying up of the 

 Lichen before the preparation was made. 



a later period upon the web of hyphae derived from the spores ; and even small rudiments 

 of a thallus were observed ; but the genetic connexion of the gonidia with the germinating 

 filaments has not been made clear \ The mode of germination of the very large spores 

 of some genera, Megalospora, Ochrolechia, and Pertusaria, differs from that of all the 

 rest. They are simple, not septate, and densely filled with drops of oil (Fig. 194, A, B). 

 Each spore puts out from different parts of its circumference in germination a great 

 number, even as many as a hundred, germinating filaments. The formation of each 

 begins with the appearance in the endospore of a cavity widening from within outwards, 



* [Tulasne believed that he twice detected the formation of gonidia upon the hyphoe : Ann. 

 des Sci. Nat. 1852, vol. XVII, p. 96.— Ed.] 



