58 On the Reaction of Iodine in Lichens and Fungi. 
that species has red-chestnut hands. It is more like C. Moloch, 
and may be a variety of it; but it differs greatly from Geoffroy 
and Dahlbom’s description. 
Callithriz castaneoventris, n. sp. 
Fur dark blackish grey, minutely punctulated with grey ; out- 
side of the limbs reddish-washed; forehead, hands, and feet 
black ; whiskers, throat, chest, belly, and inside of the limbs 
dark-red chestnut; tail black, tip washed with white; hair of 
tail black the whole length, except near the end, where the tips 
of the hairs are white. 
Hab. Brazils. 
VI.—Notule Lichenologice. No. I. 
By the Rev. W. A. Letcuron, B.A., F.L.S. 
On the Reaction of Iodine in Lichens and Fungi. 
In his earliest writings on Lichens, and down to the present 
time, Dr. W. Nylander, one of the most accurate and learned of 
European lichenologists, has shown that the application of an 
aqueous solution: of iodine affords a very useful aid in the exa- 
mination and determination of Lichens, especially the inferior 
ones. By a chemical reaction the solution produces a change of 
colour either in the gelatina hymenea, or the spores, or the 
thecze, or the thallus. This reaction is a coloration of these 
parts, either of a blue colour or of a vinous red (as in Agyrium 
rufum, Fr.); or if at first a blue is produced, it almost immediately 
changes in some instances into a vinous red. If the reaction 
does not take place, the parts remain simply colourless or be- 
come of a yellow tinge, similar to the colour of the solution it- 
self. This reaction is constant ; and although no reliance can be 
placed on it in the way of an isolated character, still it is highly 
useful as a valuable and unfailing confirmatory one, when com- 
bined with others, either external or internal. Such a chemical 
difference, however, indicates an organic difference worthy of 
investigation, and which might be otherwise overlooked. 
This chemical reaction occurs just the same, whether the 
specimen of the lichen be recently or long since gathered. 
But the same is not always the case in Fungi; for Dr. Nylan- 
der gathered near Helsingfors, in Finland, a specimen of Peziza 
Polytrichii, Schun., which perfectly agreed with the figure in 
‘Fl. Dan.’ t. 1916. fig. 1, in which the gelatina hymenea in a 
living state became intensely blue with the solution of iodine. 
But on examining the same specimen two years afterwards, the 
iodine produced no reaction, the gelatina hymenea remaining 
