18 MISCELLANEOUS PUBLICATION 955, U.S. DEPT. OF AGRICULTURE 



classification of the Myxomycetes is the monograph of the North Amer- 

 ican species by Martin (21 ) . 



LICHENS 



Lichens are an unusual group of micro-organisms, because each one 

 is always composed of two separate living components; namely, a 

 fungus and an alga living in association with each other to give the 

 gross appearance of a single plant. Even though two micro-organ- 

 isms are involved, they are named as a single plant. 



In many lichens special outgrowths are formed, which are composed 

 of a fungal mycelium and a few algal cells that together act as a repro- 

 ductive body. The fungus component is usually an ascomycete, most 

 often a form belonging to the Discomycetes. The fungus typically 

 reproduces by forming ascospores. A few lichens have their fungus 

 components as basidiomycetes. The algae usually belong to the blue- 

 green or to the green algae. The component organisms have been 

 grown independently of each other. 



Typically, lichens grow on soil, trunks and branches of trees, and 

 rocks. Rarely are they found in water. Many problems of their 

 nutrition and growth are unsolved. 



According to one authority, there are about 400 genera and 16,000 

 species of lichens in the world. Two references on the classification 

 of these organisms are by Zahlbruckner (29) and Fink (9) . 



Lichens produce a variety of lichen acids and pigments like litmus. 

 In the Far North some lichens are utilized for food by grazing animals. 



RELATIONSHIP OF TAXONOMY TO 



TECHNOLOGY ] 



In the mid-1940's microbiological studies in pure culture on growth, 

 physiology, and products, except for pathogens, were limited to a 

 small number of bacterial genera and less than 12 genera of fungi. 

 Only a few soil microbiologists had ever investigated saprophytic 

 actinomycetes. To the fermentologist then, genera such as Ustilago, 

 Curvularia, and Wojnowicia were unknown. Twenty years later the 

 diversity of micro-organisms used in microbiological investigations 

 appears to parallel roughly the tremendous research activity and in- 

 dustrial development in the field of microbiology. Developments in 

 the antibiotic, vitamin, and steroid fields have made it necessary to look 

 at all kinds of micro-organisms not hitherto investigated. 



It is necessary in any microbiological research group to have a col- 

 lection of a great variety of micro-organisms and to have at least one 

 person supervising it who is versed in their identification and ecology. 

 This combination is necessary for two reasons. First, to keep a collec- 

 tion of micro-organisms vigorous and pure, someone needs to be famil- 

 iar with their appearance and know the salient species characteristics. 

 Second, to obtain more diverse and new types of organisms without 

 repetition, a taxonomist is needed who is intimately acquainted with 

 the habitats of micro-organisms in nature. Undoubtedly new devel- 

 opments will depend largely on the discovery of new strains of micro- 



