R. B. CKorr— OX A THEORY OF LICHENS. 167 



porfoct darkness, and after some time foimd that mixed with the 

 J'rofoeoccHS-cclU there were fragments of what appeared to he the 

 mycelium of a fungus. After a furtlier deprivation of light for 

 some time, I foimd that the mycelium had greatly increased in 

 quantity, and that it surrounded and imprisoned the perfectly 

 healthy still cells of the Protococcus. 



In this condition you Avill see it under my microscope this 

 evening. At the October meeting of this Society I showed the 

 Protococcus, then freshly gathered, when many of the cells were 

 motile, now they are all stationary, though a few retain the hyaline 

 envelope. Yoii will observe that all or nearly all the cells are red, 

 and that although under a high power (700 diameters) no connexion 

 with the fungus can be perceived. Therefore we have what the 

 advocates of the theory declare a lichen to be, viz. an alga sur- 

 roimded and imprisoned by a fungus, only it is in water instead 

 of air. Probably further study would prove that the presence of 

 the fungus was accidental, and that though the Protococcus is 

 apparently healthy, it is not increasing by either of its known 

 methods of growth. As this inquiry can be easily prosecuted by 

 any one possessing a microscope with a ^-inch objective, I hope 

 some of you will try the exceedingly simple experiment detailed 

 above, and if you can get as far as I have got, that you will en- 

 deavour to induce the dual growth to flourish in air as well as 

 water. I would also suggest that one phial be kept in the light and 

 another in the dark, in order that wc may find out whether that 

 has anything to do with the fungal growth, or whether it is only a 

 coincidence. 



