260 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



are sent off in a vapory cloud just at tlie very time that the 

 young leaves of the maples are expanding, and numerous 

 difficulties of epiphytous Fungi may be satisfied by similar 

 phenomena. The facts adduced by Dutrochet, that alkaline 

 and acid substances produce different moulds, are simply expli- 

 cable by the same principle on which certain plants are pecu- 

 liar to salt marshes. Many other instances occur of the deve- 

 lopment of moulds in closed cavities, into which it was 

 scarcely possible for spores to penetrate from without. The 

 strongest case I have met with is the development of a 

 yellow mould within the cerebral cavity of Golden Pheasants, 

 which soon proved fatal. Enough has been brought for- 

 ward to make at once the difficulties and probable solu- 

 tion of the question apparent. If it be once allowed that 

 matter may traverse closed tissues derived from spores capable 

 of reproducing a species, the gi-eater part of the difficulty 

 ceases. 



258. The productions found in anomalous situations, are 

 very often those which have the widest range, and are the 

 most abundant in individuals, and when it is remembered how 

 much more capability there is in many Cryptogams than in 

 PhjEnogams, of resisting extremes of temperature, we shall 

 be ready, provided our minds be free from prejudice, to ascribe 

 apparent mysteries to natiu-al causes.* One of the most 

 striking cases, perhaps, is the development of moulds from the 

 globules of milk. Without laying too much stress on the 

 difficulty of following up the development of a single globule 

 amongst a multitude, there can be no reason why spores of 

 Penicillium, or at least particles capable of reproducing it, 

 should not be present in the milk as well as the Oidium in 

 diabetic urine. And though the true spores are of consider- 

 able size, it is more than probable that many moulds, as, for 

 instance, such as grow on paste, decaying meat, vegetables, &c., 



* Those wLo wish to see the statements of a recent advocate of spon- 

 taneous generation and its cognate theories, may consult De Gros' 

 memoir, Ann. d. Sc. Nat. 3 ser., v. 17, p. 193. At the commencement 

 of his memoir, he eliminates several productions which have no claim 

 to be considered as either animal or autonomous. 



