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American Gooseberry Mildew. 



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Description of the Fungus. — There are two well-marked 

 stages in the life of this fungus : in the first stage it is 

 white (See Journal, May, 1907, Coloured Plate facing p. 

 104) ; in the second stage it is brown (See Journal, December, 

 1907, Coloured Plate facing p. 544). The white stage always 

 comes first, but the brown is more easily seen and is often 

 the first to attract attention. The white form of the 

 mildew, usually called the summer stage, may appear at 

 any time between May and November, while the brown 

 stage, known as the winter stage, may be seen from July 

 onwards. During the winter months the brown colour 

 gradually changes to grey. While in the white stage the 

 mildew produces vast numbers of minute spores. (The 

 spores of fungi correspond to the seeds of higher plants.) 

 These spores are carried about in various ways, and if they 

 fall on the opening buds or young fruit of a gooseberry 

 bush they begin to grow at once. In this way in warm and 

 moist weather the mildew may spread very rapidly ; but for- 

 tunately for fruit-growers it does not always spread rapidly. 

 The summer spores, though numerous, are short-lived, and 

 in cool, dry weather they seem to be incapable of doing much 

 mischief. 



If gooseberry mildew were to depend on the short-lived 

 summer spores it could not exist throughout the winter; 

 very soon, therefore, a second kind of spore. begins to form. 

 This spore is known as the winter or resting spore. The 

 fungus is thus more difficult to check than an ordinary weed, 

 which produces only one kind of seed, and the difficulty is 

 increased by the character of the winter fruits inside of which 

 the spores are found. 



Before forming winter spores the mildew changes colour 

 and assumes a deep brown tint, so that badly-affected twigs 

 look as if they had been smeared with chocolate. If infested 

 twigs are thereafter examined with a magnifying glass 

 minute black dots called winter fruits will be seen. (The 

 winter fruits are shown in Fig. 4 of the second Plate men- 

 tioned above.) Each winter fruit consists of a strong shell, 

 inside which are eight spores. The shell protects the delicate 

 spores throughout the winter, and does not open until spring 

 growth begins. From the course which the disease runs in 

 this country, it would appear that the fruits begin to liberate 



