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ditions, it is highly absurd for Hchen systematists to enter into 

 lengthy and detailed descriptions of species, varieties, subvarieties 

 and even forms. As Fimfstiick states, " Bei der ausserordentlich 

 schvvankenden Abgrenzung der Arten bei den verschiedenen 

 Autoren ist es geradezu unmoglich eine sichere Orientierung 

 uber die Arten zahl zu gewinnen." His further statement that 

 there are in all probability thus far not more than 4,000 good 

 species known harmonizes with the estimates of several other 

 lichenologists. Contrasting this very fair estimate with the fact 

 that some 20,000 species, varieties and forms are actually de- 

 scribed it is very evident that there lies an enormous task before 

 those who will attempt to balance this difference. Special care 

 will be necessary in the study and revision of the lower groups. 

 For example, over 100 species, varieties and forms of Vcrriicaria 

 are described. It is more than likely that there are not half that 

 number of good species. This applies also to the genus ArtJio- 

 nia as well as to other genera. It may be advisable in some 

 instances to subdivide certain genera. It would appear that 

 Zahlbruckner gives too much systematic importance to the thecial 

 characters, which is however to be expected from one who recog- 

 nizes the lichens as modified fungi. Too much systematic impor- 

 tance is ascribed to the pycnoconidial apparatus (spermogonia), 

 since the function and occurrence of this organ or structure is 

 but little understood. In brief the subject of lichen classification, 

 as understood at the present time maybe summarized as follows : 



1 . While some authorities are satisfied that lichens deserve to 

 be recognized as an autonomous group, others are not ready to 

 admit this. This difference of opinion docs not cause any serious 

 confusion in the conception of lichen groups and species. 



2. There is great confusion with regard to the delimitation of 

 lichen species. The number of good species is in all probabil- 

 ity less than one fifth of those actually described. 



3. The system of classification proposed by Zahlbruckner is ex- 

 cellent and should be generally adopted. This would very mate- 

 rially facilitate the work of studying the various groups more care- 

 fully, thus perfecting our knowledge of lichens more and more and 

 making it possible to form a more perfect system in the near future. 



Cai.iiornia Coi.legk of I'marmacy, San Francisco. 



