CALYPTOSPORA GOEPPERTIANA 61 



which they completely fill. They are mostly divided by two 

 crossed walls into groups of four cells, each provided with a 

 germ-pore at its upper and inner corner. 



In the spring following their formation, they germinate in 

 situ about May, sending out their basidia through the dead 

 epidermis, and producing their basidiospores in the air. These 

 are blown by the wind on to the just-starting shoots of Fir, and 

 infect the young leaves, on which they produce the secidia on 

 yellow spots in two rows, one on each side of the midrib. The 

 a?cidia are cylindrical, white, with torn margin, ^ — 1 mm. high, 

 filled with orange spores, and when empty look like the remains 

 of insects' eggs. Their spores are soon ripe and can infect the 

 young Cowberry shoots, but not the Fir. The diseased leaves 

 soon turn yellow and begin to fall off during July ; it is this 

 early defoliation of the Fir that does the harm. 



There is obviously no cure except to remove and burn the 

 infested Cowberry plants, and for the sake of prevention these 

 should be searched for in the neighbourhood, when a plantation 

 of Silver Fir or its allies is going to be made. There is no 

 difficulty in detecting them on account of the peculiar appear- 

 ance which they present. The disease is rare in this country, 

 and is confined mainly to the moorland districts. 



These life-histories have been selected in such a way as to 

 show, so far as could be done from British species, the remarkable 

 variations that exist in the cycle of development and in the 

 occurrence of the different spore-forms of the Uredinales. 



