170 



The' Canadian Horticulturist. 



GOOSEBERRY MILDEW. 



Sir, -Could you in the Canadian Horticulturist say exactly what the mildew is, if 

 it effects onlj the leaves, or the leaves and fruit of the gooseberry, and if there is any 

 remedy for it '.' A Subscriber, Montreal, Que. 



S HIS mildew, according to Scribner, belongs to the same general 

 class of fungi as the powdery mildew of the grape. It has the 

 specific name of Sphaerotheca mors-uvae. It attacks its host only 

 on the surface, giving the exterior a whitish, powdery appearance. 

 The slendt;r filaments of the fungus throw out growths which 

 draw nourishment from its host, and finally send out upright 

 growths which form oblong cells by means of a division wall across the top. 

 See Fig. 535. These cells are summer spores, and each one is capable of 

 immediate germination. They are pro- 

 duced as described, in large numbers, 

 and this accounts for the rapid spread 

 of the fungus in the summer time, the 

 spores being very easily carried about in 

 every direction by the wind, even to 

 very distant places. In Fig. 535 the 

 upright branches are shown as at a, and 

 the summer spores in process of forma- 

 tion by division at b, one or two having 

 fallen off. Each of these will quickly 

 germinate if they" lie in a moist place 

 during the heat of the summer, the first 

 movement being to throw out horizontal 



threads, to be succeeded by the upright ones, thus repeat- 

 ing the life history as as above described. 



This mildew first attacks the young half-grown leaves 

 and ends of the young shoots, and very soon after, patches 

 of the same may be found upon the fruit itself. 



In order to enable this evil fungus to survive, there is 

 another class of spores called winter spores. In the case 

 of the powdery mildew of the grape, these are not mature 

 until late in the season, but in the gooseberry mildew 

 they are found in maturity as early as the month of June. 

 Fig. 536, a and b represents two filaments uniting, 

 and soon after, the one at b becomes swollen, and then it 

 assumes the form of Fig. 537, and is called the perethe- 

 cium. This, when mature, contains sacs of winter spores, 

 or asri. and on account of the pressure from within, it 



Fi<;. 535. 



Fig. 536. 



Fig. 537 



