occurring in Living Beings, 375 



spots of mildew a certain number of the filaments, which were 

 erect, were isolated from the felt, and terminated by a round- 

 ish agglomeration of greenish sporules. In subjecting these 

 straight filaments to a high power of the microscope, it was 

 noticed that some of them supported sporules with a capitu- 

 lum, whilst others terminated in a flat margined disk, which 

 appeared to be the mode in which those filaments terminated 

 which had lost their sporules. Sometimes these filaments ap- 

 proximated each other, and formed irregular meshes at the 

 surface of the spots of mildew, sometimes they looked like 

 cylindrical masses. After the most careful examination it 

 could never be discovered that any thing like rooty fibres pene- 

 trated into the albuminous layers. 



Many questions here naturally occur concerning the rela- 

 tions which must subsist between the mould and the false 

 membrane which supports it. Is it developed after the mem- 

 brane has been secreted, and find in it a substance of organic 

 origin, though not living, which is analogous to that upon 

 which it is so often developed in the open air I or does the 

 mould precede the formation of the false membrane, which is 

 only the result of the irritation produced at the surface of the 

 normal membrane, and owes its life to the roots of the mil- 

 dew l or, finally, are the mould and false membrane propa- 

 gated simultaneously I This last method appears the most 

 probable, 1*^, Because no spot of false membrane was ever 

 noticed which was not also covered with mould ; and 2d, Be- 

 cause no mould was ever seen which was not separated from 

 the natural surface by a false membrane, whose consistence al- 

 ways corresponded with the extent and age of the Cryptogamia. 

 Hence it would appear that whenever a sporule of mould, or 

 the propagating cause of this singular vegetation whatever it 

 may be, was attached to the surface of the living membrane, 

 the spot, being excited, immediately became the site of an 

 albuminous deposit upon which the mould began to grow, ex- 

 tending its fibriles towards an indefinite circumference, and 

 inducing the formation of a false membrane from the normal 

 one, whose extension corresponded with that of the plant ; the 

 addition of new albuminous layers from beneath explains the 

 increased thickness of the central parts of the false membrane. 



