1 1 



Cane sugar. (Commercial.) Growth similar to that in glucose. 



Cellulose. (Pure cellulose filter paper was used in sufficient amount 

 to soak up the liquid.) Growth vigorous at the start, though on the 

 whole not quite as vigorous as on glucose and cane sugar. 



Starch. (Commercial corn starch.) The best growth from the 

 beginning. The undissolved starch in the bottom of the flask was 

 observed to decrease materially, while the mycelium seemed to grow 

 down into it in a compact mass. It is evident from this result that 

 starch is easily available to the Fusarium as food, probably, it was 

 thought, by a rapid conversion of the starch into glucose by the 

 means of diastase excreted by the fungus. 



To investigate this matter more fully, a concentrated solution of 

 starch was made by taking a small amount of starch and allowing it 

 to stand in water for a day. A mycelium extract was then prepared 

 by grinding a considerable amount of the mycelium in a mortar with 

 a small amount of clean sand. Water was then added, the whole 

 poured off the sand and allowed to stand for a day or more. The 

 liquid was then decanted and used. Five cubic centimeters of the ex- 

 tract was added to twenty cubic centimeters of the starch. In one flask 

 the extract was boiled, and in another unboiled. After a number of 

 days two cubic centimeters of a very dilute solution of iodine was 

 added to each flask. In each case a deep blue color was obtained, if 

 anything lighter in the unboiled flask. As it was evident from cultures 

 that starch is readily utilized by the fungus, some of the starch solution 

 was inoculated with the Fusarium. After a week's growth, the iodine 

 test was again tried. In this case, there was no reaction, showing 

 that all the starch had been converted and utilized by the fungus. 



One of the reasons for the preceding cultural experiments was to 

 ascertain, if possible, why the fruit became infected at an early stage 

 only, while the rot failed in every case to increase after the tomatoes 

 were more than about i}( inches in diameter. 



The result of the starch experiment would seem to throw some 

 light on the subject. If Fusarium solani grows particularly well on 

 starch, it would naturally develop while the starch is present in 

 greatest abundance. However, this does not explain why the rot 

 never appears on fruits nearly or fully grown, but which have not 

 lost their chlorophyll. The malic acid experiment suggested a pos- 

 sible clew to this. If, as shown by the experiment, the acid, when 



