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of threads which spread tliroiigh tlie fluid, and from the threads 

 erect stems arose, bearing at their tips the well-known blue 

 conidia of Penicillium glaucuni. Thus the cycle of its growth 

 was completed, first by the formation of a sclerotium derived 

 from the conidia in wliich a process of conjugation Avas observed, 

 the result being the formation of ascogones, or ascigerous tubes 

 bearing asci and sporidia ; and next by the reproduction of the 

 mould, or conidia bearing threads, from these sporidia. This 

 experiment was repeated several times ; but in no case did any 

 other form of fungi occur to give sanction to the theory of 

 polymorphism. The result was here also negative, as regards the 

 I'onuection of yeast cells with Penicillium ; and the same 

 observation holds as in the case of Eeess's experiments ; nor can 

 the positive evidence derived from Mr. Berkeley's accourit be 

 discredited by the iailures of Reess and Brefeld. 



Notwithstanding the negative results of Brefeld's experiments 

 with Penicillium glaucum, so far as regards its supposed 

 polymorphism, the truth of the theory has been demonstrated in 

 numerous cases by Tulasne and others ; it may therefore be of 

 interest to give instances presenting positive evidence of the 

 correctness of their views. 



The Genus Isaria will furnish us with a case in point : — Isaria 

 farinosa (Fr.) consists of a floccose body from a quarter to one 

 inch in height, branched at the summit, and there clothed with 

 a coat of white spores, termed conidia ; it grows on the gi'ound in 

 woods, and, if dug up with care, it is found to proceed from a 

 chrysalis, or caterpillar buried in the soil ; it was long considered, 

 and was described by Fries as an autonomous species, i.e., as a 

 plant complete in itself. Tulasne traced its develojjment, and 

 found it to be merely an early stage of a much more complex 

 species, Sphceria militaris of the Flora Danica. In the summer it 

 appears in its conidiiferous state, but as the Avinter comes on small 

 prominences appear on the upper part of the branches, one of 

 which tlien swells out and assumes a club shape ; the 



