254 PLANT DISEASES 



not only present a very dissimilar appearance, but also 

 grow as parasites on different plants at different periods 

 during the completion of their life-cycle. The fungus 

 under consideration causes spindle-shaped swellings on the 

 branches oi Juniperus communis, and during the months of 

 April and May numerous flattened, gelatinous masses of 

 a pale orange colour, and about half an inch in length, 

 ooze out of these swollen places. The gelatinous out- 

 growths consist of myriads of reproductive bodies called 

 teleutospores, imbedded in mucilage. When the teleuto- 

 spores are mature, they commence to germinate at once, 

 without falling away. 



Each spore produces two long, slender branches or 

 germ-tubes, each of which bears two or three very minute 

 secondary spores near its tip. The mycelium of the fungus 

 is perennial in the juniper branches ; consequently, when a 

 branch is once infected, a crop of spores is produced each 

 spring, the diseased patch becoming larger each succeed- 

 ing year, as the mycelium spreads in the branch. This is 

 as far as the development of the fungus proceeds on the 

 juniper. The minute secondary spores, when mature, are 

 scattered by wind, insects, etc., and those that happen to 

 ahght on the damp surface of a living leaf, young shoot, 

 or fruit of the hawthorn, or on the leaves of the pear or 

 the whitebeam, germinate at once, the germ-tube enters 

 the tissue of the living leaf, and in about three weeks' time 

 from the period of inoculation produces the second form 

 of fruit of the fungus, known as the aecidium stage, which 

 bursts through the tissue of the leaf under the form of 

 clusters of minute, horn-shaped bodies. These bodies are 

 hollow, open, and slightly fringed at the tip, and are filled 

 with minute round bodies capable of germination, called 

 aecidiospores. Finally, the aecidiospores only germinate 



