ANTHRACNOSE OF CUCURBITS. 19 



Cellulose may also be utilized as a sole source of carbon. Pure 

 cellulose jelly prepared from absorbent cotton and substituted for 

 sucrose supported a growth of mycelium which yielded in several 

 months a dry weight greater than that of the cellulose added. Fur- 

 ther proof of the ability of Colletotrichum to dissolve cellulose was 

 furnished by the clearing of the turbidity in an unslanted test tube 

 of cellulose agar to a depth of 1 cm. beneath the colony. This sug- 

 gests that a cellulose-dissolving enzym was secreted, which acted in 

 advance of the mycelium. In a similar tube containing sucrose in 

 addition to the cellulose, growth was more vigorous, but little or no 

 visible disappearance of the cellulose was noted. This indicates that 

 the presence of sucrose may have inhibited the utilization of cellu- 

 lose. 



EFFECT OF COPPER SULPHATE. 



Using the full nutrient solution, the influence of very low concen- 

 trations of copper sulphate upon the growth of Colletotrichum and 

 Aspergillus was studied. Colletotrichum proved to be much more 

 sensitive to copper sulphate. Whereas Aspergillus showed marked 

 increase of yield in a concentration of molecular -r- 16,000, toxic effects 

 in molecular -f- 1,000 and ability to grow in the presence of molecular 

 -T- 250, Colletotrichum was only stimulated slightly, if at all, by con- 

 centrations of copper sulphate as low as molecular -r- 128,000 and 

 showed toxic effects in molecular -r- 64,000 and total inhibition of 

 growth in molecular -f- 2,000. 



SPORE GERMINATION. 



In poured plates of agar at room temperature, spores germinate 

 within five hours. In drops of distilled water on slides at room tem- 

 perature, germination usually occurs within 24 hours, although this 

 time varies greatly. In some cases abundant germination occurred 

 within 10 hours and appressorium formation within 20 hours. In 

 pipette-dropper inoculations of leaves in the greenhouse, it has been 

 found that abundant appressorium formation occurred within 24 

 hours. 



In general, germination is favored by the presence of some nutrient 

 material and a 2 per cent dextrose solution or a prune decoction made 

 by steaming 10 grams of prune flesh in 1,000 c. c. of distilled water 

 has proved very useful. An abundant oxygen supply seems quite 

 essential. Germination is more prompt about the edge of drops con- 

 taming spores and is more vigorous in exposed drops than in Van 

 Tieghem cells. 



To determine the effect of such factors as temperature, food supply, 

 and aeration upon germination, a series of tests was run. This con- 

 sisted of a quadruplicate series of hanging drops in Van Tieghem cells 

 and exposed drops on flamed slides in prune decoction and in dis- 



