PRACTICAL WORK 183 



layer of tissue. Scrape off a small portion of the pustule, 

 mount in a drop of water and examine with the high power. 

 Draw some of the spherical conidia formed by the club-shaped 

 hyphae (conidiophores). 



(2) In cross-sections through a pustule (sections should be 

 cut in alcohol and mounted in dilute glycerine) note the layer 

 of closely packed chains of conidia perpendicular to the surface, 

 and the mycelium in the tissue of the host. 



(3) In sections through older pustules note the oogonia, each 

 containing a fertilised egg (zygote) in the interior of the tissue 

 of the host. 



Fungi Parasitic on Animals. 



(4) From the dead fly or ant's " egg " (pupa) infested by 

 Saprolegnia ' (which attacks both living and dead aquatic animals) 

 scrape off a small portion of the surface, mount in a drop of water, 

 and cover. Under the high power note the hyphs, and the 

 long club-shaped sporangia containing spores (which afterwards 

 escape and swim in the water as zoospores, settling and germinat- 

 ing on other living or dead aquatic animals). 



(5) If available, examine demonstration specimens of other 

 parasitic fungi growing in the bodies of fish or of aerial insects 

 (flies, caterpillars, etc). 



(6) Examine slides showing the spores of ringworm [Microsporon) 

 on the bases of human hairs. 



" True " Rust Fungi. 



(7) The wheat (or other grass) leaf provided bears orange or 

 reddish pustules produced by the rust fungus Puccinia. Examine 

 first with a hand lens and then place the leaf dry on a slide and 

 examine with the low power. Note that the surface layer of 

 the leaf is burst along the line of the pustule, which is formed of 

 masses of spores (uredospores). Scrape off some of these and 

 examine under the high power in a drop of water. Draw one or 

 two spores and look for thin places in the wall through which 

 germination will take place. 



(8) Examine similarly the leaf-bearing " aecidium cups " 

 formed by close-set chains of spores (aecidiospores) cut off from 

 ends of hyphae in the leaf. This is another stage of a rust fungus 

 (Puccinia). 



(9) Examine any fresh or museum specimens of other parasitic 

 fungi that may be available. 



I Easily obtained by keeping dead flies or ants' " eggs " in water 

 brought in from a stagnant pond containing much organic debris. 



