Necrosis of the Grape A^ine. 



337 



and removed to a sterilized me- 

 dium in a test tube (Fig. 53), 

 they soon grow and develop a 

 felted grayish white growth. 

 After a period of time, ranging 

 from two to six weeks, new 

 pycnidia will be formed which 

 have the same structure and 

 bear spores identical with the 

 ones from the original stem. 

 This process constitutes what is 

 known as making a culture. 



Now the presence of myce- 

 lium in the diseased grape stem 

 may be demonstrated without 

 the aid of a microscope and at 

 the same time the identity of 

 this mycelium with the fruiting 

 bodies on the surface estab- 

 lished. The process is another 

 culture method. If the stem of 

 a diseased vine be split open 

 carefully, in order to pre- 

 vent contamination from the 

 propagative bodies of molds, 

 mildews, etc., which are lodged 

 in the bark or are floating about 

 in the air, and a small portion 

 of the interior removed with 

 sterile instruments to a tube 

 containing sterilized grape stems 

 or some other nutrient medium, 

 in a few days a felted grayish 

 white vegetable growth or mold 

 will spread out from the chip 

 thus transferred and grow on 

 the sterile stem (Fig. 53). The 

 general appearance of the 

 growth is identical with that de- 

 scribed as having spores for its 

 origin. Such cultures also de- 

 velop fruiting bodies after the 

 usual period of time and these 



Photo. Aug. 20, 1908 



Pig. 54. — Worden. Shows progress of the 



disease front a first wire crown; root crown 



still healthy. {Same vine as is shown in 



Fig 43) 



