156 REPRODUCTION 



devoted a great deal of attention to lichen fructification and he also thought 

 that fertilization must take place within the tissue of the lichens. He 

 regarded the soredia as the true seeds, while allowing that a second series 

 of seeds might be contained in the scutellae (apothecia). 



A distinct advance was made by Hedwig 1 , a Professor of Botany in 

 Leipzig, towards the end of the eighteenth century. He followed Tourne- 

 fort in selecting Physcia ciliaris for research, and in that plant he describes 

 and figures not only the apothecia with the dark-coloured septate spores, 

 but also the pycnidia or spermogonia which he regarded as male organs. 

 The soredia, typically represented and figured by him on Parmelia physodes, 

 he judged to be " male flowers of a different type." 



Acharius 2 did not add much to the knowledge of reproduction in lichens, 

 though he takes ample note of the various fruiting structures for which he 

 invented the terms apothecia, perithecia and soredia. Under still another 

 term gongyli he included not only spores, but the spore guttulae as well as 

 the gonidia or cells forming the soredia. 



Hornschuch 3 of Greifswald described the propagation of the lower lichens 

 as being solely by means of a germinating " powder"; the more highly or- 

 ganized forms were provided with receptacles or apothecia containing spores 

 which he considered as analogous to flowers rather than to fruits. The im- 

 portant contributions to Lichenology of Wallroth 4 and Meyer 5 close this 

 period of uncertainty: the former deals almost exclusively with the form 

 and character of the vegetative thallus and the function of the " reproductive 

 gonidia." Meyer, a less prolix writer, very clearly states that the method of 

 reproduction is twofold: by spores produced in fruits, or by the germinating 

 granules of the soredia. 



B. FORMS OF REPRODUCTIVE ORGANS 



From the time of Tournefort, considerable attention had been given to 

 the various forms of scutellae, tuberculae, etc., as characters of diagnostic 

 importance. Sprengel 6 grouped these bodies finally into nine different types 

 with appropriate names which have now been mostly superseded by the 

 comprehensive terms, apothecia and perithecia. A general classification on 

 the lines of fruit development was established by Luyken 7 , who, following 

 Persoon's 8 classification of fungi, and thus recognizing their affinity, summed 

 up all known lichens as Gymnocarpeae with open fruits, and Angiocarpeae 

 with closed fruits. 



a. APOTHECIA. As in discomycetous fungi, the lichen apothecium is 

 in the form of an open concave or convex disc, but generally of rather small 



1 Hedwig 1784. 2 Acharius 1810. 3 Hornschuch 1821. 4 Wallroth 1825. 



6 Meyer 1815. 6 Sprengel 1804. 7 Luyken 1809. 8 Persoon 1801. 



