CARPOSPORE^. 
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. 
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 
