Glycogen, a substance related to starch and sugar, is found in the Fungi and Cyanophyceae as a food reserve.
Within the cytoplasm are found manifestations of functional activity, in the form of digestive vacuoles, granules, fat, glycogen, pigment, and foreign bodies.
Glycogen is formed by the action of a ferment on the carbohydrates - the starches being converted into sugars.
The significance of glycogen in large amounts, or of its absence from the tissues in pathological conditions, is not clearly understood.
Maltose, malt-sugar, maltobiose, C12H22011, is formed, together with dextrine, by the action of malt diastase on starch, and as an intermediate product in the decomposition of starch by sulphuric acid, and of glycogen by ferments.
- Fungi, like other plants, are often found to store up large quantities of reserve materials (oil, glycogen, carbohydrates, &c.) in special parts of their vegetative tissues, where they lie accumulated between a period of active assimilation and one of renewed activity, forming reserves to be consumed particularly during the formation of large fructifications.
Invisible to the microscope, but rendered visible by reagents, are glycogen, Mucor, Ascomycetes, yeast, &c. In addition to these cell-contents we have good indirect evidence of the existence of large series of other bodies, such as proteids, carbohydrates, organic acids, alkaloids, enzymes, &c. These must not be confounded with the numerous substances obtained by chemical analysis of masses of the fungus, as there is often no proof of the manner of occurrence of such bodies, though we may conclude with a good show of probability that some of them also exist preformed in the living cell.
In other forms a substance (probably glycogen or amylo-dextrin) which turns brown with iodine has been observed.