840 
Journal of Agricultural Research 
Vol. XXX, No. 9 
various types of media. In section 
Roseum longer and slenderer conidia 
are produced on rice and oatmeal agar 
than on other media more favorable 
to sporodochial development. Because 
of these differences, it is necessary 
to pay particular attention to the 
average size of different types as grown 
upon different media and under differ¬ 
ent conditions. A comparison must 
be made only of conidia produced under 
comparable conditions and between 
comparable sporulation types. 
Often the identification is difficult 
because certain species persistently 
produce only a microconidial stage. 
In such instances some special methods 
must be employed to induce the 
fungus to develop macroconidia. For 
instance, in the case of F. chenopodinum 
(Thum.) Sacc. only the comma-shaped 
spore (fig. I, D) may be observed for 
a long time. However, by repeated 
transfers of occasionally found macro¬ 
conidia, finally normal macroconidia 
can be obtained in abundance. These 
conidia enable us to identify the fungus 
with ease. It is important to empha¬ 
size that, in this species as in some 
others, often an intermediate type of 
macroconidia is produced when the 
fungus is in a semimycelial stage of 
growth and when sporodochia are 
underdeveloped. These conidia in F. 
chenopodinum (Thum.) Sacc. can easily 
be taken for those of F. sambucinum 
Fuck. Generally the microconidia in 
themselves do not represent definite 
enough characters to be used for iden¬ 
tification. 
In those doubtful cases where nor¬ 
mal macroconidia are not readily 
produced the presence of chlamy- 
dospores may be of extreme import¬ 
ance for determining the group. The 
presence or absence of chlamydospores 
makes it possible to separate species of 
section Elegans with terminal chlamy¬ 
dospores from section Lateritium 
with no chlamydospores, even though 
their macroconidia may be similar 
when grown under certain cultural 
conditions. 
The presence of ascigerous stages in 
some of the sections is of additional 
help in the identification of the imper¬ 
fect or conidial forms (9, 11). A num¬ 
ber of ascomycetes (Nectria, Calonec- 
tria, Hypomvces, Gibberella) have 
been grown from the ascospores in pure 
culture and developed the conidial 
stage, thus showing the relationship. 
In other cases cultures of Fusaria col¬ 
lected from nature have developed 
perithecia. 
Color characters on various media 
rich in carbohydrates afford a fairly 
reliable means of placing the fungi into 
sections. The color of conidia and 
stroma especially represent an impor¬ 
tant complex for identification. 
The ordinary procedure in determin¬ 
ing Fusaria is to illustrate and measure 
normal spores and a few exceptions that 
show the variability and changes with 
increasing age. The standard magnifi¬ 
cation used for the drawings is 1-1000 
for the spores and 1-500 for parts of 
sporodochia showing conidiophores and 
formation of spores. Smaller magnifi¬ 
cations may be used for special pur¬ 
poses, such as groups of sporodochia, 
sclerotia, and stroma erumpent. For 
a short study water mounts are prefer¬ 
able. In order to prevent moisture 
from escaping during the procedure of 
drawing, the edges of the cover glass 
may be waxed. Another method ( 7 ) of 
preparing slides, which has the ad¬ 
vantage of placing all the spores in 
one plane and holding them in place, 
is to make the mount on a very thin 
(0.5 mm.) sheet of agar placed on the 
slide. These agar sheets can readily 
be prepared by pouring clear agar 
between glass slides set the required 
distance apart. This method is very 
convenient for photographic purposes. 
CLASSIFICATION OF THE FORM- 
GENUS FUSARIUM 
The form-genus Fusarium includes 
all hyphomycetes and conidial stages of 
ascomycetes that have no black or 
pure gray color either in mycelium or 
in conidia and that have macroconidia 
that are acrogenous, typically septate, 
sickle-shaped, and not round at the 
ends. Microconidia, chlamydospores, 
and sclerotia may be present. Some 
Fusaria have been proved to be conidial 
stages of certain Hypocreaceae, such as 
Nectria, Hypomyces, Gibberella, and 
Calonectria. The fungi of the form- 
genus Cylindrocarpon, formerly con¬ 
sidered as Fusaria, have Nectrias and 
certain Hypomyces ( 8) as perfect stages. 
Some of the species of Ramulara or 
similar fungi as Septomyxa also form¬ 
erly placed under Fusarium, have as 
their perfect stage Neonectria (10, 11) 
and Mycosphaerella (11). The fungi 
parasitic on scale insects and possessing 
sickle-shaped to fusoid conidia are re¬ 
ferred to the genus Microcera, which 
is said to be the conidial stage of 
Sphaerostilbe. 
GROUPING OF FUSARIA IN SECTIONS 
Many Fusaria readily fall into sepa¬ 
rate groups possessing similar charac¬ 
ters. These groups are called sections, 
which, on the basis of their apparent 
