I36 BOTANY. 



the color or appearance of the leaf in the spots where the mycelium is 

 seated ? * Try to remove some of the mycelium with a needle, to see that 

 it consists of threads which are on the surface of the leaf. 



Fruit bodies. Observe the minute black specks seated on the mycelium. 

 Are all of them black, or dark in color ? If there are any yellowish ones 

 how do they compare with the dark ones as to size ? How do they compare 

 as to age ? With a hand lens examine them more carefully. Can you see 

 any dark-colored threads extending out from the fruit body ? Can you see 

 their form ? 



Demonstration 34. 



226. The fruit bodies.— Place a drop of water on a glass slip. Touch the 

 point of a scalpel or knife to the water and then scrape the surface of the 

 leaf gently where there are a number of the black bodies. The capillarity of 

 the water will hold some of the fruit bodies to the point of the knife. From 

 this tease off the fruit bodies with * needle into the drop of water on the 

 slip. Separate them well and put on the cover glass. 



Let each pupil examine the fruit bodies under the microscope. Note the 

 form of surface markings and the appendages. Sketch. 



227. The asci and spores which they contain. — Take this same prep- 

 aration, crush the fruit bodies by gently pressing on the cover glass above 

 them, until the fruit bodies are cracked open, and some of the sacs containing 

 the spores are pressed out (see fig. 116). Let the pupils examine and sketch 

 them. 



The gonidia may be demonstrated by using leaves where the fruit bodies 

 are not abundant, but which possess an abundance of the mycelium (see 

 fig. IIS). 



228. Fruit bodies of the willow mildew. — On the mycelium 

 there appear numerous black specks scattered over the affected 

 places of the leaf. These are the fruit bodies (perithecia). 

 When examined with a low power of the microscope, each one 

 is seen to be a rounded body, from which radiate numerous 



* If the leaves are not old the portions where the mycelium is seated may 

 be more or less yellow, showing an injury ; but if the leaves are quite old 

 and nearly ready to fall, the green color may have disappeared more rapidly 

 from the unaffected parts of the leaf, for the fungus gives some stimulus to the 

 leaf, and often this is manifested by the green color remaining longer in the 

 affected parts of the old leaves. 



