July IS, 191S 



Ascochyta Clematidina 



339 



Table II- — Summary of the data on the toxic effect of soap agar of various strengths on 



A scochyta clematidina 



Culture medium. 



Soap agar (i lb. to 5 

 gals.) 



Soap agar (i lb. to 

 ID gals.) 



Soap agar (i lb. to 

 15 gals.) 



Soap agar (i lb. to 

 20 gals.) 



Soap agar (i lb. to 

 40 gals.) 



Check, 2 per cent 

 agar 



Check, nutrient- 

 glucose agar 



Num- 

 ber or 

 cult- 

 ures. 



Average diameter of cultures after growth for- 



3 

 days. 



Mm. 

 O 



15 



days. 



Mm. 

 O 



O 



7 

 II 

 20 

 21 

 29 



days. 



Mm. 

 O 



O 



9 



15 



25 



29 



38 



days. 



Mm. 



II 

 19 

 32 

 40 



48 



13 IS 



days. days. days. 



Mm. 

 O 



O 



15 

 23 

 40 



SI 



60 



Mm. 

 O 



26 



44 

 61 

 69 



Mm. 



50 

 70 



77 



17 

 days. 



Mm. 



34 

 56 

 77 



days. 



Mm. 

 O 



O 

 25 



39 



67 



23 

 days. 



Mvi. 

 O 



O 



28 



44 

 73 



Plate LIV, figure 2, shows a culture of A. clematidina on soap agar. 

 The concentric ring or oily film about the culture may be 2 to 7 mm. 

 wide. Upon the drying of the medium, crystals of stearic acid are seen 

 only in this region, indicating that an active principle given off by the 

 fungus liberated the fatty acid. The culture shows a green discolora- 

 tion, which is due to the formation of brown-green, thick-walled chlamydo- 

 spores. These bodies, as well as the mycelium, are filled with oil glob- 

 ules, while none are found in the 2 per cent agar. These cultural experi- 

 ments indicate that soap at the strengths in which it is used as a contact 

 insecticide has in itself fungicidal value, as well as being a means of 

 adhesion or suspension for other materials. 



METHODS OF CONTROLLING THE FUNGUS 



The suggestions here given for controlling A. clematidina are based 

 upon the observations and experiments made in the last three years. 

 Greater success can be attained by changing the methods of culture than 

 by spraying. Long experience has taught the nurseryman that there is 

 less disease when the hybrids are supported while growing in the field or 

 in the greenhouse than when they are permitted to trail on the ground. 

 This holds true also for C. paniculata, but its selling price does not war- 

 rant so much expense for labor. This can be overcome by transplanting 

 the plants from the beds to the open field after the first year, placing them 

 far enough apart to prevent matting. Spraying is beneficial to such 

 plants, but before making such applications it is advisable to remove all 

 diseased leaves and dead vines. Plants so treated are disease-free in the 

 fall. If seedlings are grown in a greenhouse where clematis has never 

 been grown before and are kept away from older diseased beds, they will 



