128 MORPHOLOGY 



somewhat irregular. The terminal empty cells are loosely attached and as 

 they are eventually abstricted and strewn over the inside of the cup they 

 give to it the characteristic white powdery appearance. 



According to Schwendener^ development begins by an exuberant growth 

 of the medulla which raises and finally bursts the cortex; prominent cyphellae 

 have been thus formed in Sticta damaecornis (Fig. 73). In other species 

 the swelling is less noticeable or entirely absent. The opening of the cup 

 measures usually about \ mm. across, but it may stretch to a greater width. 



c. PSEUDOCYPHELLAE. In these no margin is formed, the cortex is 

 simply burst by the protruding filaments which are of the same colour — 

 yellow or white — as the medullary hyphae. They vary in size, from a minute 

 point up to 4 mm. in diameter. 



d. Occurrence and Distribution. The genus Sticta is divided into 

 two sections : (i) Eusticta in which the gonidia are bright-green algae, and 

 (2) Stictina in which they are blue-green. Cyphellae and pseudocyphellae 

 are fairly evenly distributed between the sections; they never occur together. 

 Stizenberger' found that 36 species of the section Eusticta were cyphellate, 

 while in 43 species pseudocyphellae were formed. In the section Stictina 

 there were 38 of the former and only 31 of the latter type. Both sections of 

 the genus are widely distributed in all countries, but they are most abundant 

 south of the equator, reaching their highest development in Australia and 

 New Zealand. 



In the British Isles Sticta is rather poorly represented as follows : 



\Eusticta (with bright-green gonidia). 

 Cyphellate: 6'. damaecornis. 

 Pseudocyphellate: 5. aurata. 



\Stictina (with blue-green gonidia). 

 Cyphellate: S.fuliginosa, S. limbata, S. sylvatica, S. Dufourei. 

 Pseudocyphellate: S. intricata var. Thouarsii, S. crocata. 



Structures resembling cyphellae, with an overarching rim, are sprinkled 

 over the brown under surface of the Australian lichen, Heterodea Mullen; 

 ■ the thallus is without a lower cortex, the medulla being protected by thickly 

 woven hyphae. Heterodea was at one time included among Stictaceae, 

 though now it is classified under Parmeliaceae. Pseudocyphellae are also 

 present on the non-corticate under surface of Nephromium tomentosum, 

 where they occur as little white pustules among the brown hairs; and the 

 white impressed spots on the under surface of Cetraria Islandica and allied 

 species, first determined as air pores by Zukal*, have also been described by 

 Wainio^ as pseudocyphellae. 



1 Schwendener 1863, p. 169. '^ Stizenbeiger 1895. ^ Zukal 1895, p. 1355. ^ Wainio 1909. 



