esculenta). This lichen occurs very plentifully in Algeria and Tar- 

 tary, as well as in mountainous districts of other countries. The 

 plant seems to grow and spread rapidly and, being loosely attached, 

 the wind readily carries it down the mountain-sides into the valleys, 

 where the ignorant inhabitants suppose it to have "rained from 

 heaven." Travelers in the above countries have reported several 

 noteworthy and extensive "rains of manna." The Kirghiz Tar- 

 tars eat this lichen, under the name of " earth-bread." 



Various other lichens were also used as articles of diet ; among 

 them Cetraria Islandica takes perhaps first rank, as it contains a high 

 percentage of lichen-starch (lichenin) . However, from the fact that 

 nearly all lichens contain a bitter principle which is very disagree- 

 able to the taste, they were extensively eaten only in arid countries 

 and in times of famine. 



II. PERIOD. 



From Tournefort (1694) to Micheli (1729). 



As already stated, the lichens were given no definite position in 

 the vegetable kingdom in the previous period. Under the collective 

 name " muscus " or " musco-fungi " (Morison), they were variously 

 classed as algae, fungi, liverworts and mosses. The fact which 

 separates this period from the preceding is that lichens were now 

 being looked upon as a distinct class of plants. Tournefort 1 was 

 doubtless the first to separate these plants from others and to ar- 

 range them as a distinct class under the comprehensive designation 

 "lichens." This in itself was indicative of considerable prog- 

 ress. A group of plants must be given some definite position in the 

 vegetable world before it can receive more careful study. Tourne- 

 fort was one of the few investigators of his time who believed in lay- 

 ing a foundation before beginning to build. He did not concern 

 himself so much with species-making as with a general study of 

 lichens. In all his works he does not describe more than forty-four 

 species and varieties, although fifty-six species and varieties were al- 

 ready known. This noted botanist, who was by no means especially 

 interested in lichens, devoted his limited attentions to them taken 

 collectively, and this led him to arrange them as a separate class. 



•Tournefort, J. P. de. Elements de Botanique. Paris. 1694. Institutiones Rei 

 Herbariae. Paris. 1719- 



