1896.] MICROSCOPICAL JOURNAL. 81 



do cassimilatory work if they can insure a comfortable 

 and secure abode. 



You all, 1 am sure, know that group of plants to 

 which the name of lichens is given. Many of them form 

 flat growths of various colors, covering rocks and tree 

 trunks, others hang in festoons from the dead branches 

 of hrs, or form coral or moss-like growths upon the 

 ground. The so-called cup moss, for instance, has really 

 no affinities at all with mosses, but is a true lichen. But 

 what then is a true lichen ? Well a lichen is really a 

 firm or partnership consisting of the working partner in 

 the form of a green alga and a sleeping partner, who 

 protects the alga by surrounding it with innumerable 

 threads or hyphfe, and these hyphsB tell us that this 

 second portion is of the nature of a fungus. 



That, indeed, is the case, and in a section taken through 

 a portion of a lichen you will see the green algal cells 

 lying imbedded in a mass of threads cut through in all 

 directions, and representing the filaments or hyph^e as 

 they are called of the fungus. (Fig. 2). A fungus, as 

 you see, is devoid of the green color or chlorophyll — 

 the chlorophyll which enables all green plants to take a 

 large amount of their nourislnnent — all the carbon they 

 need in fact, from the atmosphere, and to build up with 

 its help starch, which forms the starting point of other 

 organic substances. Fungi therefore are unable to do 

 this, and hence they lead either a saprophytic life, living 

 on decaying organic matter, or a parastic life, preying on 

 living animals or plants. 



In the group of the lichens however the fungus can- 

 not actually be said to have taken to either of these 

 forms of life. Here though the fungus makes use of the 

 starch and sugar formed by the green algal cells, it does 

 not in any way damage or destroy the alga, but lives 

 peaceably together with it, fostering it in fact, for its 



