4 GUIDE TO THE STUDY OF LICHENS. 



CaBsalpiuus and Camerarius, who were among the 

 earliest commentators on the writings of Theophrastus, 

 Dioscorides and Plinius, did little more than to reiter- 

 ate what was already known of lichens. At the close 

 of this century about twenty-eight species or forms of 

 lichens were described. The Scotch botanist Morison 

 (1683) described fifty-six lichens, some of which were 

 quite well figured. 



The Italian botanists were the beginners in the 

 study of the structure and growth of lichens. Mal- 

 phigi (1686) was the first to call attention to the 

 soredia, which he considered to be the true seeds of 

 lichens, since he had observed that new plants were 

 developed from them. Porta (1591) gave some very 

 crude explanations of the origin and growth of lichens, 

 which indicated that he had some fairly correct ideas 

 of the nature of these plants, while Morison, who 

 seemed to have been an accurate observer otherwise, 

 expressed it as his opinion that lichens were excremen- 

 titious matter produced by the soil, rocks and trees. 



At the close of the seventeenth century about 125 

 lichens were known and described. Especially im- 

 portant was the work of Tournefort (1694-1719). 

 This author called special attention to the apothecia 

 and some of the spores. His descriptions of the his- 

 tological characters were of necessity crude, owing to 

 the imperfections of the simple microscopes, the com- 

 pound microscope being as yet unknown. 



The systematic study of lichens really began with 

 the Florentine botanist Micheli (1729). Heretofore 

 all lichens had been placed in the one group " lichen," 



