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Ch. XL.] 



MIGEATION OF PLANTS. 



387 



Some have inferred, from the sprmging up of mushrooms 

 whenever particular soils and decomposed organic matter are 

 mixed together, that the production of fungi is accidental, 

 and not analogous to that of perfect plants. But Fries, 

 whose authority on these questions is entitled to the highest 

 respect, has shown the fallacy of this argument in favour of 

 the old doctrine of equivocal generation. ' The sporules of 

 funoi/ says this naturalist, ' are so infinite, that in a single 

 individual of Eetictdaria maxima^ I have counted above ten 



resem 



smoke ; so light that they may 



by evaporation into the atmosphere, and dispersed in so 



many 



elasticity, adhesion, &c., that it is difficult 

 place from w^hich they may be excluded.' ^ 



conceive a 



•moss 



amous 



over all equinoctial countries. It scarcely ever passes be- 

 yond the northern tropic, except in one instance, where it 

 appears around the hot-springs in the Azores, although it is 

 neither an inhabitant of the Canaries nor of Madeira. Doubt- 

 less its microscopic sporules are everywhere present, ready 



to 



■minate 



moisture 



other conditions essential to the species. 



Almost every lichen brought home from the southern 

 hemisphere by the antarctic expedition under Sir James 



^ to no less than 200 species, was ascer- 



amountin 



them 



hemisph 



cosmo 



comparatively limited ran^re of most 



phsenogamous species, we cannot fail to perceive how inti- 



ma 



their powers of dispersion. But, in order to 



see a con- 



enomena, we must first assume 



each species has one birthplace, and that it has radiated 



* Fries, cited by Lindley, Introd. to Nat. Syst. of Botany. 



c c 2 



