SYSTEMS OF CLASSIFICATION. 75 



biotic association of a fungus and an alga. Lichens, 

 therefore, have a double affinity, being closely related 

 to the fungi on the one hand and to alga^ on the other. 

 Their true position is between the fungi and algae. 

 They are a class of the cryptogaraic (flowerless) plants 

 devoid of stem and leaves. We have already discussed 

 some of the structures of lichens which are analoirous to 

 certain structures of higher plants. This analogy does 

 not indicate any close natural relationship. Lichens 

 have no roots, leaves, branches, vascular tissue, epi- 

 dermis, etc., as we find them in higher plants ; the 

 analogies are indeed very remote. 



The present tendency in classification is to proceed 

 from the lowest to the highest, from the less special- 

 ized to the more specialized, rather than from the 

 highest to the lowest. This is the natural way, as by 

 this method one can better explain the characters 

 which indicate their relationship. 



Since lichens are treated as a distinct class and not 

 as fungi, the effort must be made to show their rela- 

 tionship to each other ; in order to do this, we must 

 also study their relationship to the fungi by endeavoring 

 to find their probable fungal ancestors. Such attempts 

 have recently been made by Reinke and others, but 

 much remains yet to be done. 



The amateur need not worry about the imperfections 

 indicated ; the systems at hand will suffice for the 

 present ; future generations will work with other sys- 

 tems. 



