FUNGI. 25^ 



above the surface of the thaUus. The mother-cells of the spores, the asci are formed 

 according to Schwendener and Fuisting, in a peculiar manner. ' Even in the young ball, 

 and among the first rudiments of the paraphyses, thicker hyphse are to be seen inter- 

 woven among the rest, rich in protoplasm, undivided by septa, and with numerous 

 ramifications ; the upright ends of the branches of these hyphae which penetrate between 

 the ends of the paraphyses, develope into club-shaped asci ; they may hence be termed 

 Ascopborous hyphcE. They are very readily distinguished from the paraphyses by their 

 membrane being coloured blue by iodine after treatment with potash-solution, while 

 that of the paraphyses remains colourless. They disappear at a very early period from 

 the lower part of the rudiment of the apothecium, and remain only in one narrow layer 

 which runs parallel to the upper surface of the apothecium, and extends below the 

 lower ends of the ripe asci. In this layer they ramify in a centrifugal direction in 

 proportion as the margin of the excipulum grows, and send out new asci among the new 

 paraphyses. The first asci appear in the centre of the apothecium ; and Schwendener 

 states that no genetic connexion exists between the ascophorous hyphae and those from 

 which the. paraphyses are derived ; the two form separate systems but interwoven 

 into one another \' The layer in which the ascophorous hyphae run is called the Sub- 

 hymejiial Layer; the hymenium itself consists of the paraphyses and the asci taken 

 together. The term Hypcthecium is given to the mass of fibres lying beneath the sub- 

 hymenial layer, and is often strongly developed through subsequent growth ; it consists 

 of hyphae the branches of which end in the hymenium as paraphyses, and of the remains 

 of the primary ball ; when mature, it can scarcely be distinguished from the excipulum. 

 The growing apothecium bulges more and more, and finally breaks through the 

 layer of thallus which covers it ; the hymenium and the margin of the excipulum 

 appear above the surface of the thallus, or the part of the thallus which surrounds 

 the excij)ulum rises and grows with it forming a bowl-like rim. Among the medullary 

 hyphcC which surround the apothecium a number of gonidia subsequently appear in many 

 Lichens, so that a gonidial zone runs beneath the apothecium. In Peltigera and Solorina 

 even the young apothecium is expanded flat, its paraphyses project vertically towards 

 the surface of the thallus, and the layer of thallus which covers them is finally lifted like 

 a thin veil. In Bxomyces, Calycium, &c., the basal portion of the hypothecium is deve- 

 loped into a long stalk which elevates the apothecium. 



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

 and in its mature state to the pcrithccium 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. 193) 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 INIegalospora), 2 or 3 or from 4 to 6 (in several Pertusariae) ; in Bactrospora, Acaro- 

 spora, 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 Ascomycetes ; very commonly they are septate and multicellular ; the exospore is 

 usually smooth and often of various colours. 



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

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



^ From the newly discovered processes in the formation of the reproductive organs of the 

 Pyrenomycetes and Discomycetes, especially from the most recent statements of Janczewski on Asco- 

 bolus furfuraceus {cf. pp. 256 and 261), it may be assumed that the tubular hyphx of the sub-hymenial 

 layer arise from a yet undiscovered ascogonium or scolecite; and that thus the apothecium of 

 Lichens is the result of a sexual process in a similar manner to the peiithecia of the Pyrenomy- 

 cetes and the fruit-cups of Peziza and Ascobolus. 



