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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. tJnfortunately, the same species may 

 have two sets of behaviour, and it is 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 value — 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 live ? Let us 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 no other plants will grow these lichens are 

 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 stady 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 kafy 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 groiv 

 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 



