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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 shrubJy 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 asthe subject bears 
upon lichens. What is their food? Remember 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 vain 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 tron— 
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 
