252 
Journal of Agricultural Research 
Vol. II, No. 4 
norm” could be found and a sufficient constancy of the spores obtained 
under constant conditions. The diagnoses based exclusively on pure 
cultures allow also a determination of the fungi from field material 'when 
the effect of different degrees of moisture and of various substrata is 
understood, when what is youth and what old age, and what is mature 
and what immature in species of Fusarium 1 are known. 
METHOD OF DIFFERENTIATION 
The genus Fusarium has a number of vegetative and spore stages, 3 
and their so-called variability may be a source of confusion. This is 
evident from the fact that transfers of mycelium produce a growth quite 
different in general appearance from that derived from spores of the 
same fungus to the s^me medium under conditions otherwise identical. 
Conidia from the outside and mycelium from the fibrovascular bundles of 
a wilted plant isolated separately and grown and studied under the same 
conditions may show differences in general appearance and still be the 
same organism. They must be regarded as the same organism if one 
form can be transformed into the other. The following may be cited as 
proof: Hundreds of wheat grains among samples sent to the Kaiserlichen 
Biologischen Anstalt fur Land- und Forstwirtschaft, at Dahlem, near 
Berlin, Germany, to determine the cause of poor germination, showed 
carmine-red spots of fungous mycelium. Numerous cultures, derived 
from epiphytic and endophytic mycelium of different seeds, yielded a 
number of fungi, such as Verticillium, Spicaria, Alternaria, Trichothecium, 
Langloisula, Ramularia, Melanospora, Eeptosphaeria, Helminthosporium, 
Gibberella, and Fusarium (three species), without an ascus stage. 
The four last-named organisms, afterwards found to be distinct, 
showed practically the same general appearance; as, for example, in a 
sterile cottony growth of aerial mycelium all four showed yellow on 
sterilized rice media and carmine red on steamed potato. Repeated 
transfers of mycelium to the same medium did not give differential 
characters sufficient to identify any one character by this method. 
In some cases a few small conidia scattered in the mycelium were 
developed, but without any constant shape that was characteristic. 
Within a month, however, some plectenchymatic bodies appeared, often 
only one or two (in a test-tube culture on potato) pushing through the 
sterile mycelium. Eater, an erubescent to orange color appeared in one 
culture and an ochreous brown color in another, especially when exposed 
to daylight. This difference gave the first striking contrast between 
1 Exsiccatae will be prepared from all of these fungi and, when completed, subcultures of the original 
Strains will be sent to any-one interested. 
8 Such expressions as "mycelial stage,” "sclerotial stage,” "sporodochial stage,” "pionnotes stage,” 
** micro-conidial stage,” etc., for the sake of convenience, are used quite generally throughout this article. 
While they are not to be regarded as true stages in the accepted sense of the word, they are particularly 
desirable terms to use in connection with a taxonomic study from pure cultures of the genus Fusarium. 
For definition of terms see Wollenweber, H. \V, (1913c). 
