EXPERIMENT STATION BULLETINS. 



335 



ago, a majority of the 

 farmers account for its 

 appearance in their 

 field by attributing it 

 to the rupture of the 

 cells, or the punctures 

 of insects allowing the 

 sap to exude and, evap- 

 orating, leave a yellow 

 deposit. If we examine 

 wheat rust under a 

 microscope, when it first 

 appears, we shall find 

 great numbers of ellip- 

 tical spores of a yellow- 

 ish color, covered with 

 minute spines. These 

 are supported on short 

 stalks and have burst 

 through the epidermis 

 of the leaf. On becom- 

 ing detached they will 

 quickly germinate if 

 they happen to fall in a 

 drop of water, and if on 

 a wheat plant will pene- 

 trate the epidermis and 

 soon develop other 



Fig. 11. Puccinia graminis. Wheat Rust. SDOl'eS These VelloW 



1, section of barberry leaf, showing the aecidium fruits below and ji i 



epermagonia above ; 2, unopened aecidium fruit; 3, three summer spores are the Ul'edo Ol* 

 (uredo) spores and one teleutospores; 4, germinating uredospore ; 5, „„ ^f fU A 



cluster of winter (teleuto) spores; 6, germinating teleutospore, with oLUiiLUtJi fejjuiets ui nie 

 sporidia forming at the end of the promycelium ; 7, sporidia formed ; j-^g-f; ( Fi°" ll 3 .) 

 8, sporidia germinating on the under side of a barberry leaf and pene- T .' } sv ■"• "/ 

 trating the epidermis. —After De Bary. It the Same Wheat 



leaf be examined during the fall, the rust spot will be seen to 

 have become brown or black. The microscope will show the color 

 to be owirii>; to the presence of spores utterly unlike the yellow summer 

 spores. They are dark-colored, two-celled, and have a thick, smooth cell 

 wall and, as their function is to carry the fungus over winter, they are 

 known as winter or teleuto spores. (Fig. II, 5 , 6 .) In the spring, if 

 placed in moisture, these throw out slender threads, at the ends of which 

 button-like protuberances are formed, known as sporidia. (Fig. II, 6 , 7 .) 

 Under proper conditions these will develop into a new fungus, but, strange 

 though it seems, they will not develop on the leaves of wheat plants, 

 although they propagate readily on the leaves of the barberry. Let us 

 follow it and sea what comes of it. The upper side of the barberry leaf 

 soon becomes yellow, and if the spot on the opposite side is examined 

 there will be found a beautiful, cup-like cavity rilled with thousands of 

 minute golden spheres, arranged in chains (Fig. II 1 ,), known as jecidi- 

 ospores. If these be placed on the leaves of wheat, the characteristic 

 rust will be produced. 



Years ago, it was the belief of farmers in England and in the older 

 states of this country, that if barberry bushes were near wheat fields 

 there would be a great amount of rust, and with our present knowledge 



