SPERMOGONIA 



207 



Lichen "spermatia" also differ very strikingly from the male cells of any 

 given group of plants in their very great diversity of form and size; but the 



a 



Fig. 115. a, spermatia; d, hypha produced from spermatium of 

 Buellia functiformis Th. Fr. x 950 (after IstvanfE). 



chief argument adduced by the opponents of the sexual theory is the capacity 

 of germination that has been proved to exist in a fair number of species. It 

 is true that germination has been induced in the spermatia of the Uredines by 

 several research workers — by Plowright', Sappin-Trouffy^ and by Brefeld^ — 

 who employed artificial nutritive solutions (sugar or honey), but the results 

 obtained were not much more than the budding process of yeast cells. Bre- 

 feld also succeeded in germinating the " spermatia " of a pyrenomycetous 

 fungus, Polystigma rubrunt, one of the germinating tubes reaching a length 

 four times that of the spore; but it is now known that all of these fungal 

 spermatia are non-functional, either sexually or asexually, and degenerate 

 soon after their expulsion, or even while still in the spermogonium. 



c. Influence of Symbiosis. In any consideration of lichens it is 

 constantly necessary to hark back to their origin as symbiotic organisms, 

 and to bear in mind the influence of the composite life on their development. 

 After germination from the spore, the lichen hypha is so dependant on its 

 association with the alga, that, in natural conditions, though it persists 

 without the gonidia for a time, it attains to only a rather feeble growth of 

 mycelial filaments. In nutritive cultures, as Moller has proved, the absence 

 of the alga is partly compensated by the artificial food supply, and a scanty 

 thalline growth is formed up to the stage of pycnidial fruits. Not only in 

 pycnidia but in all the fruiting bodies of lichens, symbiosis has entailed 

 a distinct retrogression in the reproductive importance of the spores, as 

 compared with fungi. 



In Ascomycetes, the asci constitute the overwhelming bulk of the 

 hymenium ; in most lichens, there are serried ranks of paraphyses with 

 comparatively few asci, and the spores are often imperfectly developed. 

 It would not therefore be surprising if the bodies claimed by Moller and 

 others as pycnidiospores had also lost even to a considerable extent their 

 reproductive capacity. 



1 Plowright 1889. 2 gjjppin.Xrouffy 1896. ^ grefeld 1891. 



