. i- ■. 01 CUKKKN l IM skai.viiks l;l.l,ATl . 



meristeuial nchyma, of vvliich the roundish cells are closely united, 



almost without interspaces j the upper cells remain as cortical tissue, the 

 lower cells grow oul into hyphae. A mong the cells which are to form the 

 gonidia] zone newgonidia arise, and in single cells of this tissue the blue 

 mr appears. These oewly-formed blue-green gonidia are at 

 first surrounded by colourless cells, but by increase in numbers they 

 come to live in groups among the loose hyphal tissue. Blfving decides 

 thai these coloured cells have the same origin as the colourless, and are 

 nol differenl organisms. 



He repeats these observations on Everina prunastri, the gonidia of 

 which belong to Gystococcus. In spring he found numerous colourless 

 cells or gonidia which had all been transformed by the end of May into 



n cells ; intermediate stages can be traced. Originally they were 

 formed as the end cells of short hyphal branches, and can often be seen 

 in situ, but they separate easily. Blfving further states that he has 

 never seen hyphae penetrate the gonidia. He allows that there is a gap 

 in his observations ; he is not sure that he has seen the first begin- 

 nings of a gonidium, but probably they are formed as colourless cells 

 in late autumn or in winter. He has, however, demonstrated the 

 occurrence of colourless gonidia in Anaptychia ciliaris, Ramalina pur- 

 puracea, Usnea barbata, and Cladina rangiferina. 



Culture of Lichen Gonidia.* — Ernest Hayren, a pupil of Blfving, 



has also 1 n studying the lichen thallus. He rinds that the gonidia 



{Gystococcus) are smaller in Ramalina than in Everina, and divide more 

 frequently. In E. furfuracw they form colonies, in E. prunastri they 

 are more scattered. Hayren cultivated small portions of the thallus as 

 well as soredia on various culture media in damp chambers. The greater 

 the illumination, the more cell-division occurred among the gonidia, 

 which finally became free from hyphte. The new cells were formed in 

 - or multiples of 8 within the mother-cell, and became free by the 

 breaking down of the enclosing cell-wall. Swarm spores were formed 

 when any change was made in the illumination from dark to light or on 

 any weakening of the culture solution. They are pear-shaped, with two 

 equal cilia at the foremost end. 



The colourless cortical cells of the thallus grow very slowly in culture 



solutions, and produce a mycelium. If grown in the dark the mycelium 



finally predominates over' the gonidia. The hyphae of the medulla do 



nol develop further. The dark brown lower cortex of E. furfuraem 



developed in sugar solution a mycelium, which on being transferred to 



bark decoction produced spore-balls formed by repeated cell-division 



and interwoven growth of the hyphae. In 'these balls are formed 



mmute round spores, the whole interior of the balls finally falling into 



rtrich germinate readily in sugar solution. Growth in this case 



soon, but if gonidia are added, mycelium revives quickly, 



hen transferred to bark decoction forms again spore-balls. 



Ih- mycelium cultivated from soredia of E. furfuraem also forms 

 ills in bark decoction. Mycelium from the soredia of Ramalina 

 fartnacea forms similar balls. 



Porh. Nordisk. Naturf.-och Liik., xvi. 7 Helsingfors (1903) pp. 31-2. 



