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THE VICTORIAN NATURALIST. 201 



species, or even any genus. One lesson taught us by our study 

 of nature is that we should be humble in our judgments, and 

 always ready, on the production of new facts, to re-consider the 

 terms of any conclusion to which we have come, however 

 cautiously we may have arrived at it. All scientific knowledge 

 is tentative. I would, therefore, urge the student not to be 

 -afraid of humbly exercising his own judgment, and not to be 

 disheartened if he find that he has to modify his conclusions 

 again and again. A case occurred lately within my knowledge 

 in which a number of specimens of a Victorian lichen were 

 submitted to a lichenologist of no mean repute ; but the 

 specimens were all sterile. They were decided by him to be a 

 new species, which was named accordingly. Some time after- 

 wards further specimens were received, but with the fruit on 

 them, which showed clearly that the supposed new species had 

 long been known as a European and American lichen ; and the 

 lichenologist frankly said — " The name I gave seems now, in 

 presence of the perfect specimen, to be very wide of the mark.'* 

 Although the beginner ought not to attempt the naming of a 

 lichen which is imperfect, yet, with a typical and complete 

 specimen before him, he should exercise his own powers of 

 observation and discrimination upon it before he submits it to 

 another person to be named. 



If there is any doubt whether a plant be a lichen or not, this 

 question can be, in nearly all cases, very readily and decidedly 

 answered. Take a minute portion of the youngest part of the 

 thallus and put it on a microscopical slide with a drop of water. 

 Then, with a knife, bruise down the piece of lichen till it is all 

 apparently dissolved. Put a thin glass cover on it, and submit 

 it to the 27Sth power of a microscope. If it be a lichen there 

 will be seen numerous green or yellowish spheroids, either 

 simple — when they are called granula gonima — or enveloped in 

 a tunic — when they are called gonidia. These are peculiar to 

 lichens, and their presence is decisive of the plant in question 

 being a lichen. 



The classification which I have given in this paper will 

 enable the student to decide, in most cases without difficulty, as 

 to the family to which a specimen belongs. To determine the 

 tribe and genus will require more careful and minute examina- 

 tion ; and to fix the species will often take some time and close 

 comparison with well-named specimens, such as those in the 

 Melbourne Botanic Museum which bear the signature Mull. 

 Arg. 



This work will also require the aid of some book giving a 

 descriptive classification of lichens. I am sorry to say that 

 there is absolutely no descriptive list of Victorian lichens. 

 There is a book which has been published by Dr. William 



