The first investigators who entered into a scientific study of lichens 

 were Wallroth 1 and Meyer. 2 It is remarkable that the more important 

 works of these authors should appear in the same year. Their ob- 

 ject was not to collect and classify, but, rather, to study and compare 

 the material already at hand. Of the two investigators it is gener- 

 ally conceded that Wallroth had the clearer insight into the nature of 

 lichens, though in many respects he was not so careful an investigator 

 as Meyer. The student of lichenology will however find, to his sorrow, 

 that Wallroth's style is very involved. Each sentence contains a long 

 series of parenthetical clauses which makes it very difficult to 

 follow him. His terminology is also new and requires a special 

 study. In spite of all these objectionable features, the work is cer- 

 tainly epoch-making. Wallroth was the first author to give us some 

 knowledge of the vegetative propagative cells (Brutzellen = gonidia) . 

 He dwelt at considerable length on the "metamorphoses" of the 

 thallus as well as on its general morphology. He demonstrated that 

 some lichens were " homoemerous " and some " heteromerous " (these 

 two terms are about all that have been retained of Wallroth's termin- 

 ology) . He made a careful study of the soredia and found that they 

 consisted of gonidia enclosed by a delicate network (hyphae), and 

 held the opinion that the gonidia, hence also the soredia, could develop 

 into new plants. Under unfavorable circumstances the gonidium or 

 soredium will not develop into a lichen, but simply form a green coat- 

 ing over the substratum. Though many of the conclusions were er- 

 roneous, it must be borne in mind that this was the first attempt at a 

 scientific study of lichens. It is also much to be regretted that this 

 author did not make use of the compound microscope; in some in- 

 stances there is no evidence that he used even the simple lens. 



Meyer's studies were perhaps more comprehensive than those of 

 Wallroth. He entered into a careful consideration of the structure 

 and metamorphosis of the thallus and apothecia, the gonidia and 

 spores, the relation of lichens to the substratum, the growth and nu- 

 trition of lichens, etc. Meyer believed in the spontaneous genera- 

 tion {generatio originaria) of lichens which was stoutly denied by 

 Wallroth. Wallroth believed that the gonidia and spores were the 

 only reproductive organs of lichens. 



■Wallroth, F. W. Naturgeschichte der Flechten. Frankfurt-am-Main. I. 1825. II. 

 1827. 



2 Meyer, G. F. W. Die Entwickelung, Metamorphose und Fortpflanzung der 

 Flechten, etc. Gottingen. 1825. 



