ON FUNGI. 195 



not take place. Thus, for example, the germinations of seeds 

 will not commence until the concurrence of such quantities of 

 water, oxygen, and heat as are necessary to fulfil the conditions 

 requisite to their growth, but immediately the conditions are ful- 

 filled germination takes place, as a matter of necessity. The 

 seed has no option whether or not it will grow, but grow it must 

 when the conditions are satisfied ; similarly with the sporules of 

 Fungi, until the requisite conditions are fulfilled they do not grow, 

 but immediately on their fulfilment, they must grow, and do 

 grow. This then will explain why certain Fungi are meteoric ; 

 at a particular state of the atmosphere only are the requisite con- 

 ditions to the growth of their sporules fulfilled, till then they lie 

 dormant. 



The 3rd objection merely shews that the conditions of growth 

 of the sporules of Agaricus campestris are ascertained to be ful- 

 filled when a certain mixture of organic and inorganic matter is 

 exposed to certain states of the atmosphere, and that other Fungi 

 do not grow too, simply proves that their growth depends upon 

 different conditions from those on which the growth of Agaricus 

 campestris does. That certain Fungi are produced but upon one 

 kind of matter proves that there are, and there only are the con- 

 ditions of growth of those Fungi satisfied; and that they are 

 produced constantly shews the infinite number of sporules there 

 must be distributed over the face of the earth. Fries has counted 

 in a single individual of one small Fungus above 10,000,000 spo- 

 rules ! In some general observations on their number, he says, 

 "the sporules are so infinite, so subtle (they are scarcely visible to 

 the naked eye, and often resemble thin smoke,) so light, (raised 

 perhaps by evaporation into the atmosphere,) and are dispersed in 

 so many ways by the attraction of the sun, by insects, wind, elas- 

 ticity, adhesion, &c, that it is difficult to conceive a place from 

 which they can be excluded." (Fries, Elevch., 158.) 



The sporules of an hundred different sorts of Fungi may be 

 mixed in the matter of which the mushroom bed is made, or on 

 the leaves, or in the cheese, but those only will vegetate whose 

 conditions of growth are satisfied, which are different in each 

 case. We have exactly parallel instances in Phoenogamous 

 plants, where certain plants will grow only on certain soils, as on 

 chalk, or in water, we have no difficulty in believing this, because 

 we can put it to the test of experiment. We see certain Fungi 

 confined to certain substances, and yet we refuse to admit the 



