PUCCINIA. 305 



of uredospores. Scrape one of these dark patches, and 

 note the dark brown spindle-shaped teleutospores, often 

 showing at one end part of the slender stalk on which 

 the spore was borne ; the two cells have thick walls, 

 showing two layers (exospore and endospore). Note the 

 pit in the wall of each cell of the teleutospore in the 

 upper cell the pit is at the apex, in the lower it is at one 

 side just below the cross-wall separating the two cells. 



Also examine sections across the patch; both uredo- 

 spores and teleutospores may be seen, since the two kinds 

 of spores are produced by the same mycelium. 



438. Germination of the Uredospores. Place uredospores 

 in a hanging drop of water or of Pasteur's solution, and examine 

 each day until germination occurs. Note that a hypha may 

 grow out from either or both of the pits or germ-pores. Also 

 try to infect Wheat plants, as follows : Grow Wheat in pots of 

 soil out of doors, to get healthy young plants with leaves about 

 10 cm. long ; bring in fresh Wheat leaves well covered with the 

 rusty patches, and tie two of the young Wheat leaves together 

 with the infected leaf between them, so that the three are in close 

 contact for some length ; cover the plants with a bell-jar, keep 

 them moist, and each day examine tangential sections of the 

 epidermis for germinating uredospores, sending a germ-tube in 

 through a stoma. 



439. Germination of the Teleutospores. The uredospores 

 usually germinate promptly in summer, though they can last 

 through the winter ; but the teleutospores are essentially resting 

 spores which germinate in the following spring. They may be 

 induced to germinate in autumn, but it is better to tie together in 

 a bundle Wheat straw (stems) bearing teleutospore sori, leave 

 the bundle outdoors all winter, and in spring (March or April) 

 cut off small portions of stem with teleutospores on them and 

 place these in water in a watch-glass, keeping them under a bell- 

 glass and examining with the microscope daily until germination 

 occurs. 



Also scrape teleutospores from the patches into water or Pasteur's 

 solution in moist-chamber slides. Note that the exospore of one 

 or both cells of the teleutospore bursts, and the endospore-covered 

 contents grow out as a hypha (promycelium or basidium) which 

 divides by cross-walls into a row of four or five cells, each of these 

 (except the long basal one) then putting out a short hypha which 

 swells up at the tip and cuts off a single sporidium or basidio- 

 spore. 



p. B. 20 



