PUCCINIA , 115 



on the wheat ? When is it present in greatest quantity ? 

 What effect does it have on the host ? 



1. Scrape out the contents of a spot and examine under 

 h.p. Note the color and form of the spores, called vredo- 

 spores, or summer spores. These spores are always one- 

 celled. Draw. 



2. Study sections of the leaves (Sec. 212), as for the telentospores, and 

 note the origin of the uredospores and their relation to the mycelium 

 of the host. Show these points in a large figure. 



C. The cluster cifps on barberry. Examine the infected barberry 

 leaves, making a habit sketch of the lower side. Draw the 

 spots under a hand lens, noting (1) on the lower side rela- 

 tively large cluster cups, or wcidia, containing cvcidiospores ; 

 (2) on the upper side minute crater-like openings marking 

 the sjyermogonia. 



1. Scrape out the contents of a cluster cup and draw the 

 secidiospores under h.p. 



2. Section the spots in pith or study sections cut with a microtome 

 (Sec. 212). Note (a) the formation of the secidiospores in chains 

 from a fruiting surface ; (b) that the wall of the cluster cup, perid- 

 ium^ is a cell membrane composed of rows of modified spores 

 adhering together ; (c) the small spermogonia filled with very deli- 

 cate converging filaments which develop terminally bacterioid bod- 

 ies, believed to be degenerate sperms and called spermatia ; [d) the 

 general relation of these parts to the tissue of the host. Show these 

 points in a large figure or series of figures. 



Keference. PrincipleSj Sec. 275. 



Questions. Why are the telentospores thick w^alled ? What 

 do they develop on germination (see Principles, Fig. 231)? 

 Outline carefully the life history of the wheat rust from 

 your laboratory study and reading. Compare this life history 

 with that of the smut, noting the phases that correspond 

 with one another. Does the barberry grow in your section 

 of the country, and if so does it produce cluster cups? If it 

 does not grow there how may the life history of the rust 

 be modified? 



