62 
continue their development until the heading time of the oats, 
when the flowering parts are replaced by enormous numbers of 
black dust-hke spores. These spores are known as chlamydo- 
spores and, under favorable conditions, germinate, producing a 
short hypha, or thread, on which are developed secondary spores, 
rr econidia, It is by means of these conidia that the invasion of 
the young seedling oat plant takes place. Both chlamydospores 
and conidia, however, may be transferred to suitable substances 
n flasks, where they will give rise to characteristic growths 
which may be studied and compared one with the other. The 
appearance of three cultures of the loose smut of oats is shown in 
fieure 6, 
These cultures in flasks are interesting for a comparison of the 
behavior of the two species of smut, and also for the highly 
specialized physiologic races. The cultures may be developed by 
the isolation of single chlamydospores, or by the isolation of the 
secondary conidia, and cultures derived by different methods have 
been used in the studies. Many isolations from single chlamydo- 
spores of both loose and covered smut have been obtained. Some 
of the cultures of loose smut are very similar in their appearance, 
while others show considerable variation. The same is true of 
the cultures of covered smut. Further, many of the cultures of 
the covered smut are essentially identical with those of the loose 
smut, and it does not seem possible to clearly differentiate the two 
species by constant characteristics of the cultures. 
Comparisons have been made between the cultures of different 
races, derived from single chlamydospores. Many of the cultures 
of the same race are essentially identical in appearance, while 
others show marked differences. Further, cultures from different 
races can be selected which are remarkable for their uniformity 
and, by a proper selection of cultures, very diverse types of growth 
may be obtained. 
Many isolations from single conidia have also been made, and 
similar differences in the behavior of the cultures to those isolated 
from chlamydospores have been observed. 
Some moculation experiments have been carried out. Cultures 
of loose smut derived from single chlamydospores have been used 
o inoculate Gothlane 
4 
and Monarch oats, the former being very 
