STUDIES OF DISEASE PRODUCING SPECIES OF FUSARIUM. 225 



CULTURE STUDIES. 



On account of the fact that certain species of Fusarium show- 

 very different cultural characteristics when grown under dif- 

 ferent conditions, it is difficult to compare the forms from 

 dififerent sources unless they can be grown on the same medium 

 under the same conditions. The desirability of growing the 

 fungi which are to be compared on a number of culture media 

 should be readily apparent. 



In this w^ork comparative studies were begun with the forms 

 isolated from apples and later other fungi were included so that 

 with most of the media forms from 24 sources, F I to F 

 XXIV, were grown on each medium at the same time. This 

 number was used in comparing the effect of different sugars 

 and acids on growth and also in the studies in which fermenta- 

 tion tubes were used. 



In all of the work reported here, each form was grown on 

 at least two tubes or plates of the medium and in many cases 

 this was repeated several times. Cylinders of vegetables, as 

 potato, turnip, carrot and beet are very satisfactory media for 

 the growth of species of Fusarium. When potato cylinders are 

 prepared in the same way from time to time and the cultures 

 are kept under the same conditions in other respects there is 

 very little variation in the appearance of the mycelium of a 

 given strain. The writer has observed no striking changes in 

 the cultural characters of certain species of Fusarium which 

 have been grown upon this medium with frequent transfers for 

 four years. The species of Fusarium are usually regarded as 

 very variable, but what have been considered as variations can 

 probably be explained in every case as responses to changed 

 conditions. , 



Some of the most important characters to be made use of in 

 comparing representatives of this genus are : mycelium as to 

 amount of aerial growth and color, presence or absence of 

 chlamydospores, shape and size of conidia, and with those 

 forms which are parasitic, the extent of the parasitism should 

 be determined by means of inoculations. 



Owing to the incompleteness of many of the published 

 descriptions, these characters have little value in placing forms 

 in the described species. The amount of aerial growth and the 



