28 



has practically abandoned them as being too unreliable in their effects. 

 In Bartholow's Materia Medica (1884) we find that only Cetraria 

 Islandica is recommended to be given as a stomachic tonic, "but only 

 to be prescribed when the more efficient remedies are not well borne." 

 The homeopathic school of medicine still recommends certain lich- 

 ens in a few diseases, for example, Sticta -pulmonaria in lung 

 troubles. Other lichens are given in whooping-cough, etc. 



VII. PERIOD. 



From Reinke (1S94) to the Close of 1896. 



I may be justly criticised for recognizing this as a period, since 

 Reinke's propositions have not been generally accepted as correct. 

 It can not, however, be denied that his conclusions are based upon 

 sound argument and should, therefore, mark the beginning of the 

 period in which lichens are recognized as a distinct class of plants ; 

 such recognition being based upon physiological considerations. In his 

 article on " Die Stellung der Flechten im Pflanzensysteme " (75, III) 

 Reinke endeavors to demonstrate that lichens are autonomous struc- 

 tures. He recognizes and admits all the facts established by 

 Schwendener and his followers, but maintains that lichens are physi- 

 ologically as well as morphologically sufficiently distinct from both 

 fungi and algae to be recognized as a distinct class. Although the 

 lichen-algae may be cultivated artifically this does not indicate that 

 lichens should be considered as fungi parasitically associated with 

 algae. The fact remains that when either of the symbionts is re- 

 moved the lichen no longer exists ; its autonomy is destroyed. The 

 difference between the school of Schwendener and that of Reinke is 

 principally a difference of opinion as to what constitutes autonomy. 

 Tubeuf (96) states that in mutualism we have a union of fungus and 

 alga which produces an individual wholly different from either of the 

 components and entirely distinct as to form, requirements and condi- 

 tions of life. This intimate nutritive association of two or more 

 originally distinct organisms, which is typically met with in lichens, 

 Tubeuf designates as individualism. According to this definition 

 lichens should, doubtless, be treated as a distinct class. 



It will be remembered that Tuckerman and others of the previ- 



