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caused by some remarkable circumstances connected with their developement, 

 the most material of which are the following : they grow with a degree of 

 rapidity unknown in other plants, acquiring the volume of many inches in the 

 space of a night, and are frequently meteoric, that is, spring up after storms, or 

 only in particular states of the atmosphere. It is possible to increase particular 

 species with certainty, by an ascertained mixture of organic and inorganic mat- 

 ter exposed to well known atmospheric conditions, as is proved by the process 

 adopted by gardeners for obtaining Agaricus campestris ; a process so certain, 

 that no one ever saw any other kind of Agaricus produced in mushroom-beds ; 

 this could not happen if the Mushrooms sprang from seeds or sporules floating 

 in the air, as in that case many species would necessarily be mixed together ; 

 they are often produced constantly upon the same kind of matter, and upon 

 nothing else, such as the species that are parasitic upon leaves : all which is 

 considered strong evidence of the production of Fungi being accidental, and not 

 analogous to that of perfect plants. Fries, however, whose opinion must have 

 great weight in all questions relating to Fungi, argues against these notions in 

 the following manner : " Their sporules are so infinite (in a single individual of 

 Reticularia maxima I have counted above 10,000,000), so subtile (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, elasticity, adhesion, 

 &c), that it is difficult to conceive a place from which they can be excluded." 

 I give his words as nearly as possible, because they may be considered the sum 

 of all that has to be urged against the doctrine of equivocal generation in Fungi ; 

 but without admitting, by any means, so much force in his statement as is 

 required to set the question at rest. In short, it is no answer to such argu- 

 ments as those just adverted to. It seems to me that a preliminary examina- 

 tion is necessary into the existence of an exact analogy between all the plants 

 called Fungi ; a question which must, be settled before any further inquiry can 

 be properly entered upon. That a number of the fungus-like bodies found upon 

 leaves are mere diseases of the cuticle, or of the subjacent tissue, is by no means 

 an uncommon opinion ; that many more, such as the Byssaceae in particular, 

 are irregular and accidental expansions of vegetable tissue in the absence of 

 light, is not improbable ; and it is already certain that no inconsiderable number 

 of the. Fungi of botanists are actually either, as various Rhizomorphas, the 

 deformed roots of flowering plants growing in cellars, clefts of rocks, and walls ; 

 or mere stains upon the surface of leaves, as Venularia grammica ; or the 

 rudiments of other Fungi, as many of Persoon's Fibrillarias. Those who are 

 anxious to inquire into these and other points, are referred to Fries' works gene- 

 rally, to the various writings of Nees von Esenbeck, and to the Scottish Cryp- 

 togamic Flora of Dr. Greville. 



Geography. The Fungi by which most extra-tropical countries are inha- 

 bited are so numerous, that no one can safely form even a conjecture as to the 

 number that actually exists. If they are ever fortuitous productions, the num- 

 ber must be indeterminable ; if many are mere diseases and the remainder fixed 

 species, then the knowledge of their nature must be reduced to a more settled 

 state before any judgment upon their number can be formed. According to 

 Fries, he discovered no fewer than 2000 species within the compass of a square 

 furlong in Sweden ; of Agaricus alone above 1000 species are described ; and 

 of the lower tribes the number must be infinite. Sprengel, however, does not 

 enumerate in his Systema Vegetabilium more than between 2700 and 2800 ■ 

 but when we consider that his genus Agaricus does not go beyond number 646 

 although 1000 at least are described, it is not improbable that the rest of his 

 enumeration is equally defective, and that the number of described Fungi per- 

 haps amounts to between 4 and 5000. Of tropical species we know but little ■ 



