MORPHOLOGY. 



(figs. 208-211). These two forms occur on the stems, blades, 

 etc., of the wheat, also on oats, rye, and some of the grasses. 



402. Teleutospores of the black-rust form. — If we scrape off 

 some portion of one of the black pustules (sori), tease it out 



Head of wheat showing black rust spots 

 on the chaff and awns. 



Teleutospores oi wlieat rust, 

 showing two cells and the pedicel. 



Fig. 213. 

 Uredospores of wheat rust, one 

 showing remnants of the pedicel. 



in water on a slide, and e.xamine with a microscope, \\e see 

 numerous gonidia, composed of two cells, and having thick, 

 brownish walls as shown in fig. 212. Usually there is a slender 

 brownish stalk on one end. 'I'hese gonidia are called leleulo- 

 spores. They are somewhat oblong or elliptical, a little con- 

 stricted where tjie septum separates the two cells, and the end 

 cell varies from ovate to rounded. 'I'he mycelium of the iungus 



