26 THE DETERMTlSrATTOX OF LICHENS IN THE FIELD 



29. Algal cells Trentepolilia. Th. wliitisb, effuse, 



+ P^^'^®^'^^^^"^ ^"^ pruinose, K4- yellow 



C + rose Arthonia pruinata. 



Algal cells green 80. 



30. Common plant with whitish th. (K+ 3"ellow) 



of veiTucose granules, the aj^ices of which 



become red with C Lecanora tartarea. 



Infrequent plant with whitish, determinate, 

 smoothish th. K— C + red Pertusaria velata. 



Infrequent plant with greyish, minutely 

 squamulose th. K+ yellow C+ orange- 

 yellow Bilimbia caradocensis. 



31. Th. with a purplish or violet coloration with 



K. {Aho see Huiodiiia colobina.) Callopisma. 



Th. without a purplish or violet coloration 



withK 32. 



32. Th. whitish, with algal cells of Trentepohlia, 



and having whitish-grey globoid spermo- 



gones with large spermatia (12-16 x 



3-4 ix) Lecanactis abietina. 



Th. whitish or pale yellow (algal cells green), 



and having large black spermogones with 



small (2-3 X 1 /^ ) spermatia Biatorina granifor mis. 



Sterile plants without such characters usu. 



not determinable. 



33. Th. having a reddish coloration with C 31. 



Th. not having a reddish coloration with C . 41. 



34. Algal cells Trentepohlia. Kare. Dirina 



repanda. [Also see Lecanactis (4-5) and 

 Opegrapha grumulosa.~\ 

 Algal cells green 35. 



35. Medulla blue with iodine. Th. whitish or 



greyish K— Diploschistes (1 & 4). 



Medulla not blue with iodine 36. 



36. Th. copper- or chestnut-coloured, determinate, 



areolate K— Lecidea fuscoatra. 



Th. whitish or greyish (sometimes + green- 

 ish ) or brownish 37. 



37. Th. whitish with reddish cephalodia K— or 



faint Lecidea panaeola {j). 



Th. without cephalodia (superficial granules 



with blue-green alga^) 38. 



38. Th. yellow with K 39. 



Th. having a negative or only a faint colora- 

 tion with K 40. 



39. Th. whitish, thickish, granular-areolate ...... Lecidea latypea. 



Th. whitish, granulate-verrucose, the apices 



of the verrucas becoming red with C. 

 {Rinodina atrocinerea and Lecanora suh- 

 radiosa also occur, on . rocks and become 

 yellow with K and reddish with C.) Lecanora tartarea. 



