BY JOHN SHIRLEY, D.SC. 59 



Avas cut off, excepti such quantities as were dissolved in the 

 tap water, and the inorganic food was reduced to a 

 n;inimum. The algal cells continued beautifully green 

 throughout this experiment, and the thallus kept its 

 normal shape, but the hyphee became slimy and partly 

 lost their vitality. 



In the second case, when supplied with plenty of air, 

 such inorganic foods as can be obtained from the soil, a-ncl 

 water absorbed through thei lower cortex only, both sym- 

 bionts were able to develop normally. 



As all species of Sticta and Parmelia are provided 

 Avith upper and lower cortices, this would lead one to infer 

 that the cyphellce of Stictacese, and the absorption pores 

 of Parmeliaccce are means by which water and dissolved 

 food matters enter the thallus and are carried by the 

 hyphee to the Cystococcus cells. Undeir the conditions of 

 the second experiment, the rain water would not only 

 carry inorganic food for the alga, but also' organic matter 

 from the humus of the soil, or the decay of cortical matter 

 for the support of the fungus. This last would be addition- 

 al to that taken from the alga by the haustoria of the 

 fungus. 



2. The Cortex. 



The cortex, where not carrying apothecia, sper- 

 magonia or rhizinse, usually constitutes 30-50 per cent, 

 of the thickness of the thallus. The upper cortex is usually 

 the thicker of the two' rinds, and is not seldom twice or 

 thrice the thickness of the lower covering. It takes an 

 •artificial stain better, the cells of the lower coat being more 

 deeply tinted with a natural brown or brown-black pig- 

 menti, resembling the jDhceophyll or phycophaein of the 

 brown seaweeds. The hyphee of the medulla have the power 

 possessed by conidiophores of forming chains of cells by ab- 

 striction from their extremities. Tliis power is seen in the 

 formatio'U of the coirtices, of the haustoriai surrounding gon- 

 idia, of the walls of the spermagonia, and of the sporiferous 

 hyphae. This change of hyphal threads into chains of cells 

 can well be studied in the pseudo-cyphellse of the Stictaicese, 

 whore the ends of the hypbse protrude loosely in minute 

 necklaces into the cavities of the false cyphellae, the 

 terminal cells becoming white or yellow. These coloured 

 cells were once regarded as soredia, but are only loosely 

 arranged and partly used up cortical cells. 



(A.) In the upper cortex of the Parmelias there ar© 

 three different methods in which the thickened cells may 

 be arranged. The first is shown in P. limbata, P. tiliacece 



