i8 



Journal of Agricultural Research 



Vol. XX, No. i 



room temperature, produced numerous perithecia on their exposed 

 surfaces. These matured before the end of the fourth week from the time 

 of sowing. As soon as the ascospores in the perithecia were found to 

 be mature, the kernels were sifted from the sand and preserved in dry 

 condition until needed for study or inoculation. 



The development, in the laboratory, of perfect stages of those species 

 of Fusarium which have a perfect stage was secured in the way originally 

 described by Appel and Wollenweber and later extended by Wollenweber. 

 It need only be emphasized that the perithecia of these fungi will rarely 

 be formed until the transfers and cultural work are begun from what 

 these authors call "normal" culture. Failure is bound to occur 95 times 

 out of 100 before the culture which is to be used 

 for development of the perfect stage is brought to 

 this condition. 



Once the culture is in the proper condition, the 

 next step consists in transferring it to media that 

 are known to favor the development of the peri- 

 thecia, such as stems of any kind, but especially 

 those of Melilotus alba, bean pods, etc. 



Care must be taken that the cultures on Melilo- 

 tus alba stems or other media are kept uniformly 

 moist until the perithecia are formed and the 

 ascospores in them are ripe. The presence of 

 certain bacteria in the cultures greatly favors the 

 formation and proper development of the perfect 

 forms of species of Fusarium. A certain bacte- 

 rium which was found in a contaminated culture 

 when added to cultures of Fusarium having per- 

 fect forms favored the formation of perithecia so 

 much that practically 100 per cent of the cultures 

 to which this organism was added developed 

 numerous normal perithecia, while even under best 

 conditions only a small number of the cultures to 

 which this bacterium was not added produced perithecia. What this organ- 

 ism is and whether other bacteria can produce the same result are not 

 known. 



Heretofore the whole work of producing the perfect stage of any 

 ascomycete in pure culture has been handicapped to a certain extent 

 by the fact that the cultures of such fungi dried out long before the 

 formation and ripening of the perithecia. The addition of water to the 

 cultures from time to time exposes them to contamination and varies 

 the amount of moisture in the culture considerably. To avoid this the 

 writer designed a special culture tube. This consists of a common test 

 tube, to the lower end of which is attached a bulb (fig. 2). When the 

 bulb is filled with water it will drain into the test tube as rapidly as the 



Fig. 2. — Special culture tube 

 for maintaining moisture in 

 culture. X Vi. 



