LINDSAY, ON POLYMORPHISM IN LICHENS. 3 



types of secondary reproductive organs — whether these are to 

 be designated Spermogonia or Pycnidia : 



I. White-pruinose, distinct, comparatively large tubercles, 

 e. g., in 



Pyrenothea leucocephala. 

 P. vermicelli/era. 



II. Black, lecidiiform, distinct, also comparatively large 

 organs, e.g., in 



P. corrugata. 



III. Minute or microscopic, black, punctiform or papillse- 

 form conceptacles — by far the commonest form, e. g., in 



P. aphanes. 

 P. rudis. 

 P. byssacea. 



Another source of confusion is to be found in the fact 

 that not a few Lichenicolous (parasitic) Micro-Fungi occupy 

 the positions usually occupied by Spermogonia or Pycnidia, 

 from which, moreover, they are indistinguishable externally, 

 e.g., species of the genera Sphceria and Torula. But the latter 

 are distinguishable by their sporidia or spores, or by other 

 characters supposed by fungologists, on very insufficient 

 grounds frequently, to separate Fungi from Lichens. Con- 

 fusion may arise in the same way from hchenicolous (parasitic) 

 Micro-Lichens, which are apt to be confounded with Spermo- 

 gonia and Pycnidia, e. g., species of Verrucaria or Micro- 

 thelia, Tichothecium or Pharcidia, Phceospora or Endococcus. 



A third source of difficulty is the varying definition of the 

 terms " Spermogonium, " and " Pycnidium," and the conflicting 

 views as to the relation which the one organ bears to the 

 other, more especially in respect of function. The two 

 highest living authorities on the subject of Lichen-reproduc- 

 tion, Tulasne and Nylander, differ as to the nomencla- 

 ture of the secondary reproductive organs of Peltigera, 

 which, according to the former, are Spermogonia, to the 

 latter, Pycnidia. Many of the organs Avhich I regard as 

 Pycnidia are included by Nylander and other lichenologists 

 among Spermogonia ; while Tulasne regards as Spermo- 

 gonia the conceptacles which, in association with Lecidea 

 abietina, I am disposed to denominate Pycnidia. Hence it is 

 an obvious necessity to the understanding of any question 

 afi'ecting the secondary reproductive organs of Lichens that 

 an author should render clear and intelligible his distinc- 

 tion between the groups of organs respectively designated 



