ACOTYLEDONE^E. 31 



city of life, it may be observed as proof, that plants 

 have been raised from the dust of specimens after 

 being kept in a hortus siccus for a period of forty 

 years. 



The fine dust discharged by the Fungi is also, no 

 doubt, the seminal produce ; because, how else can it 

 be so generally distributed as we find it to be in the 

 case of the common mushroom ? In the cultivation 

 of this fungus we generally keep fragments of the 

 plant itself under the name of spawn; but it is well 

 known that the mushroom may be generated by 

 merely collecting substances which are known to be 

 affected by the plant. These put together in a dry 

 place, and applying to the mass a moderate degree of 

 artificial heat, the seeds of the mushroom accidentally 

 therein are developed, and the perfect plant with its 

 edible part obtained. This fact is so constantly 

 before our eyes that specific modes of cultivation are 

 founded on it, and, being attended with success, 

 leave no doubt of the idea, that the light and almost 

 impalpable dust of the mushroom is, in fact, real 

 seed ; which is wafted around by the winds, and 

 wherever deposited under favourable circumstances, 

 germinates and comes to perfection. 



There are many microscopic species of Fungi 

 which are only discoverable by their effects. One of 

 the most destructive is the rust or blight in wheat 

 and other cereals. 





