10 CIECULAE XO. 131. BUREAU OF PLANT IXDUSTBY. 



CTTLTUHES ON CHE STXUT-TWIG AGAR. 



The chestnut-twig agar was prepared hx the following formula : 

 To 275 grams of 1 or 2 year old chestnut branches add 550 cubic 

 centimeters of distilled water and boil over an open flame for one-half 

 hour. Filter the juice and make up to 550 cubic centimeters with 

 distilled water. To 50 parts of this infusion add 100 parts of distilled 

 water and 2 per cent of agar flour. Steam for one-half hour, filter, 

 tube, and autoclave for 15 minutes at 115° C. 



Several different strengths of the infusion were tried, but the 

 formula given above proved the most satisfactory. The series of 

 cultures on this medium gave readily distinguishable differences be- 

 tween EndotJiia parasitica and E. radicalis. but growth was too slow 

 for general use. After one month E. parasitica showed numerous 

 spore masses and an abundant white surface growth, but no aerial 

 hyphae. E. radicalis showed no spore production and had consid- 

 erable white, fluffy, aerial mycelium at the upper edge of the agar. 

 At the end of two months a few of the tubes of E. radicalis showed 

 one or two spore pustules, while the others were unchanged. 



CXTLTXTRES ON PRUNE AGAR. 



Prune agar was prepared according to the following formula: 

 Take four ordinary prunes and add 1 hter of water. Boil over an 

 open flame for one hour, being careful not to break the skin of the 

 prunes. Strain through gauze, make up to the original amount with 

 distOled water, and add 2 per cent of agar flour. Steam for three- 

 quarters of an hour, filter, and tube. Autoclave for 15 minutes at 

 115° C. 



Cultures of Endotfiia parasitica 3 weeks old on this medium, —15 

 FuUer's scale, produced a great abundance of pycnidia with slimy 

 spore masses exuding, but no aerial mycelium. E. radicalis from 

 both American and European material produced few small pycnidia 

 and spore masses but somewhat more aerial mycehum, especially at 

 the bottom of the tubes. The other species were not grown on this 

 medium. 



CULTURES ON CORN-MEAL AGAR. 



Formula : To 50 grams of corn meal add 1 hter of water. Keep in 

 a water bath for 1 hour at a temperature of 5S° C, never over 60" C, 

 Filter through paper, add 1^ per cent of agar flour, steam for 1^ 

 hours, filter, and tube. Autoclave for 15 minutes at 115° C. 



Corn-meal agar made by the above formula generafly tests +3. 

 This has proved the best agar medium for the production of pycno- 

 spores. There is also a constant difference in the cultural characters 

 of the different species on this medium. This difference is, however, 



[Cir. 1.51] 



