2186 Journal of Applied Microscopy 



part of each conjugating branch. Any difference between the conjugating 

 branches in size or contents ? 



d. The absorption of ihe wall separating the conjugating tips and the sub- 

 sequent mixing of the two coenocytic protoplasmic masses. 



e. The mature zygospore suspended between the two branches. 



XXV. Etnpusa musca Cohn. Fly-cholera Fungus. 



Class, Zygomycetes. Order, Entomophthorales. Family, Entomophthoraceae. 



This fungus grows on the common house fly {Musca domestica). In the 

 autumn dead or dying tiies attacked by this fungus may be seen with greatly 

 swollen abdomens of a white color. Specimens may be preserved in alcohol. 



1. Study a fly recently killed by this fungus, under low power without a 

 cover-glass. Note the bands of short white hyphae (conidiophores) protruding 

 from between the black segments of the abdomen. Draw and describe. 



2. Tear open the abdomen with needles and mount the white contents and 

 some of the conidiophores in water. Examine under high power. Notice that 

 the mycelium has nearly absorbed the contents of the fiy's abdomen. 



3. Draw some of the conidiophores with conidia still attached: also draw 

 several of the conidia. Describe. 



XXVI. Saprolegiiia Sp. 



Class, Oomycetes. Order. Saprolegniales. Family, Saprolegniaceae. 



This fungus can usually be obtained by placing dead flies in a dish of spring 

 or pond water. After about five or six days the hyphae of the fungus may be 

 seen protruding from the body of the fly. On the tips of these hyphae sporangia 

 are developed which discharge numerous zoospores. 



1. Notice the fly in the water, surrounded by a halo produced by the mycel- 

 ium of the fungus. 



2. Mount some of the mycelium in water and examine under low power. 

 Draw a branch under high power, showing the granular protoplasm and a ter- 

 minal sporangium developing zoospores. Draw a branch showing an empty 

 sporangium. 



3. Study and draw free swimming zoospores. 



XXVII. Plasmopara viticola (B. & C.) B. & deT. Downy Mildew of Grape. 



Class, Oomycetes. Order, Peronosporales. Family, Peronosporaceae. 



This mildew causes a destructive disease of the leaves and young shoots of 

 the cultivated grape. The infected leaves may be collected in spring or summer 

 and preserved in 7<> per cent, alcohol or dried and kept in paper boxes. 

 Conidial stage. 



1. Examine a leaf carefully under the low power, without cover-glass. On 

 which side do the conidiophores appear ? 



2. Carefully scrape off some of the conidiophores with a needle or scalpel, 

 mount in water, and examine under low power. Under high power draw one of 

 the much branched conidiophores. If dry material is used the conidia will prob- 

 ably all have dropped off. One is developed at the tip of each peg-like branch 

 of the conidiophore. 



3. Draw several conidia and describe shape, size, and color. 



4. From alcoholic material cut cross sections of a part of a leaf containing 

 the fungus, mount, and under low power note that the conidiophores come out in 

 bunches through the stomata of the leaf. Draw. 



5. To what physiological class does this fungus belong ? Describe its 

 mode of life so far as studied. 



Ohio State University. JOHN H. ScHAFFNER. 



