SYMPTOMS OF DISEASE. 189 



of several fungi, the former often characterising the 

 teleutospore or aecidium stage of Uredineae e.g. 

 Aecidiiini G7'oss7ilariac the latter sometimes in- 

 dicating the presence of Chytridiaceae. 



Red spots are also caused by Gloeosporium 

 Fragariae on Strawberry leaves, Poly stigma rubrum 

 on Plums. 



Crimson spots on Apple and Pear leaves are also 

 due to Phytoptus : they turn brown later. 



Brown spots or flecks, varying in hue from dull 

 slaty brown to deep red browns, are a common 

 symptom of Fungus and Insect diseases, the colour 

 often indicating the death of the tissues, rather 

 than any special peculiarity of the action of the 

 parasite. Good examples are furnished by the 

 Potato-disease, and by Peronospora viticola, Sphae- 

 rella vitis and other disease-fungi of the Grape 

 Vine. The teleutospore stage of many Uredineae 

 also occurs in deep brown spots. 



Black spots and flecks are exceedingly common 

 symptoms of the presence of fungi, e.g. Fusicladium 

 on Apples and Pears, and the pycnidial and ascus 

 stages of many Ascomycetes e.g. Phyllachora 

 graminis. The teleutospore stages of species of 

 Puccmia, Phragmidiuni, etc., are also so deep in 

 colour as to appear almost black. 



Scab on Pears is due to the presence of Fusi- 

 cladium, which indurates the outer skin of the fruit 

 causing it to crack under pressure from within, 

 and to dry up, the deep brown to black patches 

 of fungus persisting on the dead surface. 



Black spots on grasses and sedges are caused 



