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The Museum Gazette 



together and form what might be considered a hirdt plant 

 possessing features not observable in the two separately 

 considered. 



A lichen is a compound of a fungus and an alga, the 

 latter is the host and the former its parasite. The so-called 

 " gonidia " of lichens are the algal parts and the fruit the 

 fungal portion of the plant. The fungi concerned in the 

 formation of lichens belong, for the most part, to that group 

 in which the spores are enclosed in capsules (asci), the 

 Ascomycetes. The fungi are much more abundant, as re- 

 gards species than the algae which enter into partnership with 

 them. Hence it is very probable that one alga may combine 

 with the hyphae of several fungi. It is not unusual to find 

 five or six lichens of different species growing on a stone no 

 bigger than a brick. 



It is not the seaweed group of algae that effect this remark- 

 able union with fungi, but minute species (frequenting walls, 

 bark, &c), requiring but little moisture, and capable of drying 

 up without injury. In fact desiccation is an advantage, it 

 assists their dispersal by wind. Fungus spores are also easily 

 dispersed by the atmosphere. Distribution may also be 

 effected by wind transportation of combined algal and fungal 

 elements, daughter colonies or " soredia " as they are termed. 

 They consist of green algal cells surrounded by hyphae, the 

 whole so small that a mass of them resembles a powder lying 

 on the old lichen thallus. " The partners in the lichen com- 

 munities appear to be, on the one hand, groups and filaments 

 of round, ellipsoidal, or discoid green cells belonging to plant 

 species included under the general name of Algce, and on the 

 other hand, pale, tubular cells or hyphae, which are destitute 

 of chlorophyll, and pertain to species of plants comprised 

 under the general name of fungi " (Kerner). There are 

 numerous species, assuming great variety of form. We have: 



(1) Crustaceous lichens which encrust wood, bark and stones. 



(2) Foliaceous lichens, resembling leaves with irregular, 

 wrinkled margins. They are usually joined to the matrix 



