441 



b. Culture experiments. 



Pure cultures of the fungus are easily procured by 

 taking small pièces of the membrane and transferring 

 them to a suitable médium. A still better way is to place 

 a jleaf which has been attacked in a damp glasbox; the 

 fungus then develops an abundance of airhyphae which 

 may easily he transferred purely to the nutritive médium. 

 The best médium appears to be potato-agar, prepared 

 according the follovving recipe of Appel and Wollen- 

 w e b e r : 



10 "/o of glucose 

 U % „ agar 

 1 % „ citric acid. 



It produces an abundant growth, much better than a 

 médium of only inorganic constituants. It may hère be 

 mentioned, that a fructification was never found in any 

 of my média, though I used a great variety of them ; so 

 it is necessary to give a description of the mycélium as 

 accurately as possible. 



The most typical thing of the mycel is the formation 

 of short branch hyphae, which bifurcate close to the main 

 hyphae (Fig. 7/ and j). The branches of the first order are 

 often strongly septate, so that a number of almost cubic 

 or globular cells arises (Fig. le). 



Anastomoses of the branches of the same hyphae as 

 well as of différent hyphae very olten occur. The pheno- 

 mena, hère described may be seen very clearly in coverslip- 

 cultures with coffee-decoct, nutritive agar or with water. 

 The figures 6 and la—j give a survey of the most typical 

 forms of the mycélium. At places, where a good many 

 side-branches hâve been formed, they twist together, this 

 is the origin of the knots described 'above (Fig. 6 and 7h). 

 Besides those knots hyphae spirally twisted may often be 

 found in agar (Fig. 7c). 



