MOULDS. 151 



dendroidal threads of this fungus proceed from a 

 creeping mycelium or spawn of entangled fila- 

 ments which, interpenetrates the matrix_, upon 

 which it establishes itself. Udou these threads 

 spherical bodies were long since observed by Dr. 

 Payen^ and^ under the name of Artotrogus, described 

 by Dr. Montague as a new species of fungus. Dr. 

 de Bary failed to detect oospores on the mycelium 

 of this mould_, although the organs found by Payen 

 in some sort resemble them. De Bary sought in 

 vain^ also_, for the spherical bodies described by 

 the author above named. It has been calculated 

 that one square line of the under surface of the 

 leaves is capable of producing 3^270 acrospores, 

 each of which yields at least six zoospores^ some- 

 times double that number; thus we have 19^620 

 reproductive bodies from that small space. The 

 mycelium from the zoospores is capable of pene- 

 trating the cellular tissue in twelve hours,, and^ 

 when established there^ it bursts through the 

 stomata of the leaves^ and fruit is perfected in 

 from fifteen to eighteen hours. Since the zoospores 

 are perfected and ready to germinate in twenty- 

 four hours from their being placed in water^ it 

 becomes almost impossible to calculate the myriads 

 of fungi that may be produced from a single centre. 

 Dr. de Bary has also demonstrated that the brown 

 spots so characteristic of the disease are the result 

 of the action of the spores or zoospores. By 

 placing a quantity of spores in a drop of water 



