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task of arranging the plants they have so thoroughly studied. 
Some Lichenists believe in chemical re-actions as a means of telling 
one species from another. They touch some part of the thallus 
with solution of chloride cf lime or strong solmtion of potash or 
solution of iodine, in the hope that their re-agent will “give” a 
yellow, a red, a blue, or purple, a brown, or something satisfactory 
in the way of evidence. Unfortunately, the same species may 
have two sets of behaviour, and itis not surprising that it should 
be so. Chemical tests, if reliable, would certainly very easily and 
quickly settle questions which require close and painstaking study, 
but they can hardly be held to be sufficiently reliable. Still, as 
confirmatory evidence, they are no doubt of real va/we—indeed are 
almost indispensable, because descriptions are barely sufficient when 
two small species are very much alike. It is believed that 
Chemistry has an important place in the examination of the lower 
plants. Where do Lichens Jive? lLetus rather ask ‘‘ where do they 
not live ?”” They are indeed the very outposts of vegetation. and are 
very widely distributed from the Tropics to the extreme north, Fries 
has reported upon species from 88deg. north latitude. In the most 
inhospitable regions where xo other plants will grow these lichensare 
found coating with their thin or powdery crust, large extents of 
rock and soil. These encrusting lichens are in many cases too 
thin to be cut off, so that to obtain specimens it is necessary to 
break off portions of the rock. A glance at the rocks and walls 
of our own town will illustrate this to our entire satisfaction ; but 
please do not begin your study amongst these small plants unless 
you are fond of up-hill work. The fact is that many of the lichens 
found on our walls in towns are small of their kind, consisting 
chiefly of those apothecia already spoken of, the thallus being 
almost absent. If you would have something to look at or, in 
correct language, if you would find /eafy or shrubby species, you must 
leave the smoke of towns and go where the air is pure, for lichens 
will not grow where the air is not up to the mark. This is so true 
that the lichen collector knows fairly well what kind of dis- 
trict he is in by the harvest he is reaping. He knows that his 
specimens will be stunted and poor if the air is impure. This fact’ 
points out the difficulty that besets any attempt to cultivate these 
very particular plants. Their cultivation has, as might be expected, 
been attempted, and especially for the purpose of settling if possible 
the knotty points before mentioned. Only partial success has been 
met with. Now let us proceed a step and ask what our plants grow 
upon and what they live upon. To settle the former part of the 
question is very easy, as you may find the next time you take your 
-‘walks abroad ’’ if you look at the trunks and branches of trees, 
the stems of perennial shrubs, the palings, the stones, and even the 
