Apr. 15, 1918 A Leaf blight of Kalmia latifolia 207 



IndoIv production. — ^Tests for indol were made with cultures of vary- 

 ing age in Dunham's solution by means of the nitroso-indol reaction. 

 No indol was produced at any time. 



Ammonia production. — Qualitative tests for ammonia w^ere made 

 with cultures grown in litmus milk, nutrient bouillon, and steamed com 

 meal by means of the calcium-hydroxid method. The results were posi- 

 tive in all cases, both in old and in young cultures. 



V1TAI.1TY ON CULTURE MEDIA. — The fungus can live for a consider- 

 able period in flasks of corn-meal agar or on potato cylinders, but it 

 loses its virulence rather quickly. Transfers on January 13, 191 6, from 

 corn-meal flasks made on January 29, 191 5, grew promptly; but inocu- 

 lations from these fresh transfers gave but a very small percentage of 

 infections. In another experiment, i flask out of a series of 10 almost 

 2 years old sent out from its dried pycnidial or stromatic surface aerial 

 hyphas in about 10 days after the addition of freshly prepared sterile 

 milk It was not possible to determine from what points these hyphse 

 were derived — that is, whether from the stroma or from the pycnidia or 

 spores — since the growth began below the surface of the milk and was 

 rather far advanced before it was observed. It is rather certain, hov/- 

 ever, that it was not from the old dried cirri, since 12 corn-meal flasks 

 were inoculated from some of the dried extruded spores in this flask, pre- 

 vious to the addition of the milk, all with negative results. 



Temperature relations. — The optimum temperature for growth 

 lies between 20° and 25° C. Numerous tests were made on various media 

 in all the compartments of a large thermostat. Germination will occur 

 at much higher and lower temperatures, but the production of pycnidia 

 and spores is in such cases very limited or absent. To test the effect of 

 temperature on growth, spores were germinated on steamed-potato 

 cylinders, corn-meal agar, etc., and then placed in the incubators at 

 different temperatures, the range being from 1° to 37.5° C, where they 

 were allowed to remain from two to five weeks. No growth occurred 

 below 5°. No pycnidia were formed below 12°, and none above 28°. 

 At 36° and 37.5° there was possibly a 10 per cent germination, but it v/as 

 limited to the germ tube in most cases. The percentage of germination 

 does not vary to any great extent betv/een 18° and 35°, though the 

 optimum point apparently lies very close to 25°. 



MORPHOLOGY AND TAXONOMY 



The hyphse of the mountain laurel fungus are exceedingly fine, and it is 

 located with difficulty in the tissues of its host. Nevertheless, this may 

 be best accomplished by means of horizontal sections stained by Van 

 Gieson's method. 



The mycelium is septate, very fine, frequently branching, and hyalin. 

 In the host the ends of the hyphae are a^ times much swollen. 



