404 TEXTBOOK OF BOTANY 



CHAPTER VII 



Barberry leaves should be collected when the cluster cups are at 

 their best in ordinary seasons in April or May. The leaves may be 

 pressed and dried for class use. Collect rusted wheat and other grains 

 during the summer and fall. Cedar apples may be gathered during 

 the fall and winter ; the infected leaves of apple, crab, and hawthorn 

 in the early summer months. 



1. Study infected barberry leaves and note the position and size 

 of the diseased areas. What is their color ? Are the leaves swollen ? 

 With a hand lens study carefully the diseased spots. What differ- 

 ences do you find between the spots on the upper and those on the 

 lower surface of a leaf ? Draw a portion of the upper and a portion 

 of the lower surface, showing the spots. 



2. Under the microscope study a cross section of a barberry leaf. 

 On the lower surface find a cluster cup. What is its boundary? 

 How are the spores (spring spores) borne in the cup? What is 

 the shape of a spore ? Draw a spore. 



3. In the upper surface of the leaf do you find cavities in which 

 small spore-like cells (spermatia) are produced? (The spermatia 

 themselves, being very small, will probably not be seen.) 



4. Study rusted wheat stems and leaves. What is the shape and 

 size of the patches (sori) in which the rust spores are borne ? Com- 

 pare a sorus with a cluster cup. Do the sori differ in color? If 

 so, how? Draw a sorus. 



6. Extract a portion of a light-colored sorus and examine it in a 

 drop of water under the microscope. Study the summer spores ; 

 if possible, find one still attached to its stalk. Draw a spore on 

 the same scale as your drawing of the spring spore. 



6. Examine in the same way some winter spores obtained from 

 a dark-colored sorus. Compare a winter spore with a spring spore 

 and a summer spore as to size, shape, color, and thickness of wall. 

 Draw a winter spore on the same scale as your drawings of the 

 other spores. 



7. Compare the rust of some other grain with the wheat rust. 

 Are the sori similar in all respects? Do you find summer spores 

 and winter spores ? Are they different in any way from the corre- 

 sponding spores of the wheat rust ? 



