Fusaria of Potatoes 107 



of fructification for these fungi, with " normal " spores and more or less 

 typical and brilliant color production. 12 



On the plugs made from stems of different plants, spore production seems 

 to be normal. 13 The spores are of typical and comparatively uniform shape, 

 septation, and size, without too dense granulation of the protoplasm, 

 and with a long duration of vitality. It often is found, however, that on 

 such media spores are less normal than, for instance, on a hard agar. 



Presence of the epidermis on the stem and tuber plugs seems to favor 

 production of fewer but better developed sporodochia, 14 and often lessens 

 development of aerial mycelium. 



Certain media, such as boiled rice, give a color that is typical for certain 

 related Fusaria. 



EFFECT OF LIGHT AND OF REACTION OF THE MEDIUM ON DIFFERENT 

 CHARACTERS OF FUSARIA 



As was stated in the introduction, very little systematic work has been 

 done on the ecology of the Fusaria. The few things which have been 

 found by other workers and by the writer, and which have some value 

 in the determination of these fungi, may be summed up briefly as follows: 



1. A diffuse daylight may affect color production considerably (Smith 

 and Swingle, 1904:48-49), but in most cases the effect is only slight or 

 there is almost none. It usually intensifies the colors produced by these 

 fungi. A very strong light often makes the colors somewhat duller, espe- 

 cially in the case of Fusaria producing bright red colors, these being turned 

 toward brown hues. No noticeable effect of the light was observed on 

 other characters of these fungi, although Appel and Wollenweber are of 

 the opinion that the spores are of a more normal type in the light than 

 in the dark. 



2. According to Appel and Wollenweber the reaction of the medium 

 has an especially noticeable effect on blue colors, which can appear only 

 in a medium of neutral or rather alkaline reaction. The blue color in a 

 medium of an acid reaction will appear as orange. True red colors remain 



12 This observation is apparently in some contradiction to the observatioas of Appel and Wollenweber 

 (1910:13-13), but indeed it is not so; because, judging by the " artificial " media actually used by them-, 

 their observation of unfitness of such media for study of " normal " growth of the Fusaria was based on 

 " soft " agars too rich in sugar. The writer also found that such agars produced abnormal growth. 



13 This was observed first by Appel and Wollenweber (1910), and on this observation mainly they con- 

 cluded that the only way to study the Fusaria properly is to study them on such " natural " media. 



14 This was first observed by Appel and Wollenweber (1910). 



