204 REPRODUCTION 



undertaken to prove that the lichen hyphae were purely fungal and parasitic 

 on the algae. A series of cultures were made by Hedlund 1 in order to 

 demonstrate that the pycnidiospores were asexual reproductive bodies; 

 they were grown in association with the lichen alga and their germination 

 was followed up to the subsequent formation of a lichen thallus. 



d. VARIATION IN PYCNIDIA. On the thallus of Catillaria denigrata 

 (Biatorina synothed) Hedlund found that there were constantly present two 

 types of pycnidia: the one with short slightly bent spores 4-8 //, x 1-5 yu,, the 

 other with much longer bent spores 10-20/1 x i'5/t; there were numerous 

 transition forms between the two kinds of spores. Germination took place 

 by the prolongation of the spore ; the hypha produced became septate and 

 branches were soon formed. Hedlund found that frequently germination 

 had already begun in the spores expelled from the spermogonium. In newly 

 formed thalline areolae it was possible to trace back the mycelium to innu- 

 merable germinating spores of both types, long and short. 



Lindsay had recorded more than one form of spermogonium on the 

 same lichen thallus, the spermatia varying considerably in size; but he was 

 most probably dealing with the mixed growth of more than one species. 

 The observations of Moller and Hedlund on this point are more exact, but 

 the limits of variation would very well include the two forms found by 

 Moller in Calicium trachelinum; and in the different pycnidia of Catillaria 

 denigrata Hedlund not only observed transition stages between the two 

 kinds of spores, but the longer pycnidiospores, as he himself allows, indicated 

 the elongation prior to germination : there is no good evidence of more than 

 one form in any species. 



F. PYCNIDIA WITH MACROSPORES 



Tulasne 2 records the presence on the lichen thallus of "pycnidia" as 

 well as of "spermogonia"; the former producing stylospores, larger bodies 

 than spermatia, occasionally septate and containing oil-drops or guttulae. 

 These spores are pyriform or ovoid in shape and are always borne at the 

 tips of simple sporophores. He compared the pycnidia with the fungus 

 genera Cytospora, Septoria, etc. As a rule they occur on lichens with a 

 poorly developed thallus, on some species of Lecanora, Lecanactis, Cali- 

 cium, Porina, in the family Strigulaceae and in Peltigera. 



There is no morphological difference between pycnidia and spermogonia 

 except that the spermatia of the latter are narrower ; but the difference is 

 so slight that, as Steiner has pointed out, these organs found on Lecanora 

 piniperda, L. Sambuci and L. eftusa have been described at one time as 

 containing microconidia (spermatia), at another macroconidia (stylospores). 

 1 Hedlund 1892. 2 Tulasne 1852. 



