246 THE NORTHERN MICROSCOPIST. 



Mr. Leighton says: “ Much attention has been of late devoted, 
and is still devoted to the subject of the gonidia of lichens. Two 
theories or opinions have sprung from these researches, which are 
respectively supported by great and learned savans. ‘Those whose 
studies are chiefly physiological maintain that the filamentous 
tissue of the thallus of lichens is a fungus which grows parasitically 
on an alga, which it envelopes and carries on with it in its growth 
so as to constitute the gonidia. On the other hand, true lichen- 
ologists, whilst admitting the apparent similarity of gonidia to 
certain algze, do not consider them as such, but as special organs 
of multiplication or propagation of lichens.” 
Although Professor Schwendener propounded this theory in 1869, 
and although many experiments have been made by various ob- 
servers to test its truth, opinion still is divided. Sachs, in his 
‘‘Text-Book of Botany’ (p. 262), says: “There can no longer be 
any doubt that the lichens are true fungi of the section Ascomy- 
cetes, but distinguished by a singular parasitism. Their hosts are 
algee which grow normally in damp places but not in water.” As 
many introductory works on botany are founded on Sachs’ work, 
this is repeated, learnt, and believed by many ; while on the other 
hand Dr. Nylander, admittedly the greatest Lichenologist of the 
age, terms the hypothesis “absurd,” and Dr. M. C. Cook classes 
together the advocates of the theories of Table-turning, Tichborne, 
and Schwendener. 
About three years ago I made my first attempt to build a lichen, 
or rather I found in a small phial that which advocates of the 
Schwendenerian theory would have no doubt claimed as such ; and 
as I have just repeated the experiment with the same result, I will 
briefly describe the modus operandi, in the hope that other members 
may by their observations throw further light on the subject. 
I placed a gathering of Protococcus pluvialis* in a small phial in 
perfect darkness, and after some time found that mixed with the 
frotococcus-cells there were fragments of what appeared to be the 
mycelium of a fungus. After a further deprivation of light for 
some time, I found 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 will 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 
en 
*In both cases the Protococcus was from a cast-iron shell at the base of a 
fountain in the garden of Mr. C. W. Nunn, of Hertford. Mr, Nunn has had 
this Protococcus under observation for several years, and considers it to be a 
distinct red variety. 
