CHAP.V.] the Influence of the Knowledge of Cryptogams. 215 



especially mentioned. But the most important result remains 

 to be told ; it is, that the two classes of Algae and Fungi, 

 hitherto kept strictly separate, must obviously be now united, 

 and an entirely new classification adopted, in which Algae and 

 Fungi recur as forms differing only in habit in various divisions 

 founded on their morphology 1 . 



A few words must be given here to the Lichens. They are 

 the division of the Thallophytes, whose true nature was last 

 recognised, and that only in modern times ; till after 1850 

 scarcely more was known of their organisation than Wallroth 

 had discovered in i825 2 , namely, that green cells, known as 

 gonidia are scattered through the fungus-like hyphal tissue of 

 the thallus. After Mohl's investigations in 1833, it was known 

 that free spores were formed in the tubes of the fructifications 

 (apothecia), and that a dust collected from the thallus and 

 consisting of a mixture of gonidia and hyphae was in a 

 condition to propagate the species. The genetic relation 

 between the chlorophyll-containing gonidia and the fungus-like 

 hyphae long continued to be obscure, till at last, after 1868, it 

 was shown that the gonidia are true Algae, and the hyphal 

 tissue a genuine Fungus, and that therefore the Lichens are not 

 a class co-ordinating with the Algae and Fungi, but a division 

 of Ascomycetes, which have this peculiarity, that they spin 

 their threads round the plants on which they feed, and take 

 them up into their tissue. De Bary suggested this explanation, 

 but it was Schwendener who adopted it without reserve and 

 openly declared it, as much to the surprise as the annoyance 

 of Lichenologists. It may be foreseen that their opposition 

 will yield to the weight of facts, which already leave no doubt 

 in the minds of the unprejudiced. 



Thus researches in the domain of the Thallophytes have led 



1 See Sachs, 'Lehrbuch der Botanik,' eel. 4 (1874), p. 245. 



2 Fr. \\ilh. Wallroth, born in the Ilarz in 1792, was district physician at 

 Nordhausen. He died in 1857. See ' Flora ' for 1857, P- 33^- 



