4 LINDSAY, ON POLYMORPHISM IN LICHENS. 



by him Spermogonia and Pycnidia. The distinction which I 

 recognise — and hereto append — is simply an anatomical one 

 — one of convenience. Hereafter it may prove to be coincident 

 ■with a physiological difference ; but as yet the function of 

 neither Spermogonium nor Pycnidium has been satisfactorily 

 demonstrated or determined. 



Anatomical or Structural Distinction between Spermogonia 



and Pycnidia. 



Externally indistinguishable, being similar as to site, size, 

 form, and colour ; verrucaeform, papillaeform, or punctiform 

 conceptacles, generally black, sometimes "white-pruinose ; in- 

 terior — of same or of a different colour, or subhyaline. 



I. Sperm,atia. I. Stylospores. 



1. Form. — Generally linear 1. Form. — Generally some 

 and cylindrical ; long in pro- modification of spherical [ob- 

 portion to their breadth; some- long-ellipsoid, pyriform, oval]; 

 times in exceptional cases split frequently broad in propor- 

 into two after being shed from tion to length ; variable and 

 their sterigmata ; of regular irregular ; sometimes bears a 

 form ; simple ; straight or relation to that of the spori- 

 curved. dium; sometimes multicellu- 

 lar and septate. 



2. Size. — Generally mi- 2. Size. — Usually larger 

 nute, especially as regards in all dimensions ; variable, 

 their transverse dimension, 



compared with stylospores ; 

 sometimes divide into two ; 

 otherwise uniform ; frequent- 

 ly atomic (and then mostly 

 regularly ellipsoid or sub- 

 spherical). 



3. Number. — Usually in 3. Number. — Usually less 

 myriads. numerous than the sperma- 



tia. 



4. Colour. — Always hya- 4. Colour. — Sonietimespale 

 line — devoid of colour. yellow, though usually co- 

 lourless. 



5. Texture. — Solid and ho- 5. Texture. — Vesicular or 

 mogeneous. cellular ; heterogeneous ; con- 

 tents frequently oily, or gra- 

 nular, or both. 



6. Site. — Borne on apices 6. Site. — Borne on the 



