THE MOULD-FUNGI. 127 



On the upper part of the stem ramifications appear, both the 

 branches and the principal axis ending in short conical apices. 

 The conidia are egg-shaped, 12-30 p long, and are provided 

 with a smooth, colourless membrane. In the conidia, as a 

 rule, 5-6 swarming spores are formed, which, when the conidia 

 are immersed in water, burst out, penetrating through the 

 epidermis of the leaves and grapes. The growth forms thick, 

 prominent, whitish spots on the leaves and fruit. In the 

 interior of the plant big, globular oospores (30 M diameter) are 

 formed, which have a brownish membrane, smooth or some- 

 what fluted, and are surrounded by the thin, colourless or 

 yellowish oogonium wall. This fungus causes great injury, in 

 that the grapes, according to the stage at which they are 

 attacked, either wither away or putrefy ; moreover, it destroys 

 the foliage. This species is indigenous to North America, and 

 was introduced into Europe in the year 1878 along with 

 American vines ; it has now spread to all vine-growing 

 countries. Vine growers are endeavouring to suppress this 

 pernicious parasite by the application of copper sulphate and 

 similar remedies. 



