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ground, and the moss growing on it. Notice how very convenient 

 it is to have ever so many different species on the same tree trunk. 

 First admire the shrubby kinds and then look at the spreading leafy 

 ones, then look more closely, through your magnifier if you like, at 

 the host of apothecia of the encrustiny or powdery species. You will, 

 unless the writer is out in his reckoning, soon be of an enquiring 

 turn of mind, and will be asking yourselves questions " What is 

 this white lichen ? What is this black one ? What is this greenish- 

 grey or this blusish-grey one ? What is this bright yellow one ? 

 What is this one on the smooth bark of holly and other trees that 

 looks like scribbling done by the hand ? What is this thickish 

 gelatinous plant and what the one that spreads its elegant thallus 

 over the grass at our feet ? Your queries must remain unanswered 

 as far as this evening's paper is concerned, and you must remember 

 that success will wait upon patient application. Let us now have 

 a tiny chapter on the food of plants as far as the subject bears 

 upon lichens. What is their food? Eemember how other 

 thallophytes manage matters. The Fungi, in the main, live upon 

 decaying vegetable matter, and the sea-weeds live upon the sub- 

 stances dissolved in the water. These are accepted facts. Lichens 

 no doubt get nearly the whole of their wants supplied by the rain 

 water which they absorb through their whole surface. Some, per- 

 haps are not entirely guiltless of parasitism, but they certainly are 

 not as a group parasitic plants, like the mistletoe, neither do they 

 live upon air — that is to say — they are not epiphytes as many 

 orchids are. Finding air somewhat unsatisfactory as diet, they 

 fall back upon water with its dissolved contents. A simple experi- 

 ment proves that they absorb water through their whole surface. 

 Distilled or pure water cannot minister to the needs of plant life, 

 as rain water can do, because of the dissolved contents of the latter. 

 What wonderful processes are carried on in the cells of living 

 plants ! For plant life generally, certain elements — notably iron — 

 are absolutely necessary, and certain compounds are very valuable as 

 plant food, but the processes dependent upon life are wrapped in 

 mystery, and are not to be understood even by the most careful 

 experimentalist. Clearly, lichens are well skilled in the art of 

 building up complex compounds out of the elements of a very plain 

 diet, although, as already pointed out, the gonidia are the only 

 cells that contain chlorophyll, which is so much concerned in the 

 preparation of plant food. A viscid substance resembling Gum 

 Arabic, and called Lichenine, is freely formed, and the presence of 

 this explains why a decoction of Iceland Moss is quite thick. This 

 decoction is one of the simple remedies, well known, but, perhaps, 

 beaten off the field by more recent competitors. Lichens furnish 

 food for man and beast, and in regions where, without them, there 



