Van Wisselingh[746] examined the hyphae of lichens as well as of fungi and experimented with a considerable number of both types of plants. He succeeded in proving the presence of chitin in the higher fungi (Basidiomycetes and Ascomycetes) and in lichens with one or two exceptions (_Cladonia_ and _Cetraria_). Though in some the quantity found was exceedingly small, in others, such as _Peltigera_, the walls of the hyphae were extremely chitinous. More recently Wester[747] has gone into the question as regards lichens, and he has practically confirmed all the results previously obtained by Wisselingh. In some species, as for instance in _Cladonia rangiferina_, _Cl. squamosa_, _Cl. gracilis_, _Ramalina calicaris_, _Solorina crocea_ and others, he found that chitin existed in large quantities, while in _Evernia prunastri_, _Usnea florida_, _U. articulata_, _Sticta damaecornis_ and _Parmelia saxatilis_ very little was present. The variation in the amount present may be very great even in the species of one genus: none for instance has been detected in _Cetraria islandica_ nor in _C. nivalis_ while it is abundant in other _Cetrariae_. There is also considerable variation in quantity in different individuals of the same species, and even in different parts of the thallus of one lichen. Factors such as habitat, age of the plant, etc., may, however, account to a considerable extent for the differences in the results obtained. _b._ LICHENIN AND ALLIED CARBOHYDRATES. It has been proved, as already stated, that chitin is present in the hyphal cell-walls of all the lichens examined except in those of _Cetraria islandica_ (Iceland Moss), _C. nivalis_ and, according to Wester[747], in those of _Bryopogon_ (_Alectoriae_). In these lichens another substance of purely carbohydrate nature is the chief constituent of the cell-walls which swell up when soaked in water to a colourless gelatinous substance. Berzelius[748] first drew attention to the peculiar qualities of this lichen product, and, recognizing its resemblance in many respects to ordinary starch, he called it “lichen-starch” or “moss-starch.” More exact observations were made later by Guérin-Varry[749] who described its properties and showed by his experiments that it contained no admixture of either starch or gum. He adopted the name lichenin for this organic soluble part of Iceland Moss. An analysis of lichenin was made by Mulder[750] who detected in addition to lichenin, which coloured yellow with iodine, small quantities of a blue-colouring substance which could be dissolved out from the lichenin and which he considered to be true starch. Berg[751] also demonstrated the compound nature of lichenin: he isolated two isomerous substances with the formula C₆H₁₀O₅. The name “isolichenin” was given to the second blue-colouring substance by Beilstein[752] in 1881.