FUNGI. 79 



the masses of spores appear as bright orange spots, mostly 

 upon the lower surface. The affected leaves are more or less 

 checked in their growth, and the upper surface shows lighter 

 blotches, corresponding to the areas below that bear the cluster 

 cups. These at first appear as little elevations of a yellowish 

 color, and covered with the epidermis ; but as the spores ripen 

 they break through the epidermis, which is turned back around 

 the opening, the whole forming a little cup filled with a bright 

 orange red powder, composed of the loose masses of spores. 



Putting a piece of the affected leaf between two pieces of pith so as to 

 hold it firmly, with a little care thin vertical sections of the leaf, including 

 one of the cups, may be made, and mounted, either in water or glycerine, 

 removing the air with alcohol. We find that the leaf is thickened at this 

 point owing to a diseased growth of the cells of the leaf, induced by the 

 action of the fungus. The mass of spores (Fig. 47, G) is surrounded by a 

 closely woven mass of filaments, forming a nearly globular cavity. Occupy- 

 ing the bottom of the cup are closely set, upright filaments, each bearing 

 a row of spores, arranged like those of the white rusts, but so closely 

 crowded as to be flattened at the sides. The outer rows have thickened 

 walls, and are grown together so as to form the wall of the cup. 



The spores are filled with granular protoplasm, in which are numerous 

 drops of orange-yellow oil, to which is principally due their color. As 

 the spores grow, they finally break the overlying epidermis, and then be- 

 come rounded as the pressure from the sides is relieved. They germinate 

 within a few hours if placed in water, sending out a tube, into which 

 pass the contents of the spore (Fig. 47, /). 



One of the most noticeable of the rusts is the cedar rust 

 (Gymnosporangium) , forming the growths known as "cedar 

 apples," often met with on the red cedar. These are rounded 

 masses, sometimes as large as a walnut, growing upon the 

 small twigs of the cedar (Fig. 47, A) . This is a morbid growth 

 of the same nature as those produced by the white rusts and 

 smuts. If one of these cedar apples is examined in the late 

 autumn or winter, it will be found to have the surface dotted 

 with little elevations covered by the epidermis, and on remov- 

 ing this we find masses of forming spores. These rupture the 



