Io DIVISION I.—GENERAL MORPHOLOGY. 
blue directly by a watery solution of iodine. It is a matter of course that there should 
be intermediate forms between the highly gelatinous and the non-gelatinous membranes, 
such as are found for instance among the sclerotia. To the above-mentioned examples 
drawn from the vegetative parts of the thallus must be added the organs of reproduction, 
spores and the parts which immediately produce them,—a. not less rich and varied con- 
tingent, of which more will be said in the chapters which deal with these organs. 
We know very little of the chemical composition of the gelatinous membranes 
of the Fungi. From the few tolerably precise investigations and from analyses which 
have been made it seems probable that they are for the most part composed of one or 
more carbo-hydrates or mixtures of carbo-hydrates nearly allied to cellulose, but with 
great capacity for swelling. The membranes of the Lichen-fungi (Cetraria, Ramalina, 
Usnea, and Cladonia) are changed by boiling in water into a homogeneous jelly known 
as lichenin, the dry substance of which is isomeric with cellulose. According to 
Nägeli and Löw the membranes of yeast-cells (Saccharomyces Cerevisiae), after boiling 
repeatedly in water, pass partly into a mucilage which they term ‘ yeast-mucilage’ ; 
the analysis of its dry substance gave a formula very near 3(C6 Hıo Os)+Hz2 O. 
When the membranes of the Lichen-fungi, especially Cetraria islandica, and of the 
asci of many of them are coloured blue by the direct action of iodine, the reaction is 
due to the carbo-hydrate which is mixed with the lichenin (itself not turning blue ' 
with iodine) and which can be extracted from it; its formula is also C6 Hıo Os, and 
it was named by Dragendorff Zichen-starch!. Most of the gelatinous membranes, like 
the yeast-mucilage, do not take the blue colour; they require further examination. 
The gelatinous membranes also appear to be in many cases the seats of colouring 
matters, for instance of the scarlet-red of the surface of the pileus of Amanita muscaria, 
of the yellow of Boletus luteus, and of others, so that we might conclude that the 
characteristic colours of the Fungi, with the exception of the reddish-yellow mentioned 
above, were in almost all cases confined to the membranes. But to microscopic 
examination in the cases named and in some others the colour appears so pale and 
so uniformly distributed over the whole cell, that it is difficult to decide with any 
certainty whether it belongs to the membranes or to the contents, or whether it is 
distributed uniformly through them both. 
A review of the anatomy of the membrane leads naturally to the mention of 
certain bodies, which are separated out from the cells and are imbedded in or more 
usually deposited on the membranes, or are interposed in the interstices of the 
hyphal weft; these are resinous excretions, lichen-acids, and especially calcium- 
oxalate. The lichen-acids will be noticed again in Division III. 
Resinous excretions, the histogenetic relationships of which need not be discussed 
in this place, are known in great abundance as a coating of the hyphae which compose 
the sporophores of Polyporus officinalis, the mushroom of the Larch, and form 
sometimes 79 per cent. of the mass of this plant. Bauke? found the hyphae of a 
Diplodia furnished with a brown ‘resin-like‘ covering. Zopf gives a similar account 
of species of this genus at page 48 of his work on Chaetomium which will be cited 

! Berg, Zur Kenntn. d. Cetraria islandica (Diss. Dorpat. 1872).—Nägeli u. Schwendener, Das 
Mikroskop, Aufl. z, 1877, p. 518. 
2 Pycniden, p. 35. 
