CARPOSPOREJE. 



3^5 



The perithecium of Angiocarpous Lichens is so similar in its mode of development 

 and in its mature state to that of the Xylariae, that there is no need to give an exact 

 description of it. 



The club-shaped asci of Lichens are similar in every essential point to those of the 

 Pyrenomycetes and Discomycetes; their wall is often very thick and capable of swelling; 

 the spores (Fig. 219) arise simultaneously, as in those Fungi, by free-cell-formation, 

 while a considerable portion of the protoplasm often remains unused in their production. 

 The normal number of spores is eight, although sometimes only 1-2 (in Umbilicaria and 

 Megalospora), 2 or 3 or from 4 to 6 (in several Pertusariae) ; in Bactrospora, Acarospora^ 

 and Sarcogyne on the other hand their number amounts to some hundreds in one ascus. 



Fig. 2r9.— Vertical section of a small portion of the apothecium oi Anaptychia cilia) is (X550); *n the medullary 

 layer of the thallus ; y the hypothecium, together with the sub-hymenial layer ; / the paraphyses of the hymenium, their 

 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. 



The structure of the spores is very various, but in general similar to that of the Asco- 

 mycetes; very commonly they are septate and multicellular; the exospore is usually smooth 

 and often variously coloured. 



The spores are set at liberty by moisture penetrating the hymenium; they are 

 suspended in the fluid which fills the ascus, and are expelled together with 'the fluid by 

 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 extends over the damp substratum 



