IOWA -ACADEMY OP SCIENCE 
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upon sterile straw as well as upon nutrient agar. That HelmintTiosporium 
species produce sclerotia was first noted by Hecke^ in the case of H. graminium. 
RaviY^ has observed the same thing with reference to H. teres. Noack^ 
has further proved that sclerotia are a factor in the life history of H. gram- 
ineum, while Diedicke® has proven the same thing true for HelmintTiosporium 
species occurring upon Bromus asper Mur. and Agropyron repens (L) Beau. 
PYCNIDIA. 
The next type of spores, the pycnidiospores, are present in the pycnidia. They 
occur upon sterile straw cultures that have undergone an extended period of 
dessication. After a month’s interval under the above perscribed conditions, 
grayish white masses appear which after a time form a dark interior. 
These bodies or pycnidia are on the average 300-375u wide and 450-600u long. 
Culture tubes of nutrient agar containing sclerotia and conidia, have not in a 
single instance developed pycnidia. The pycnidiospores are exceedingly small 
being ordinarily 1-1. 5u wide and from 2-4u in length. The walls are thin and 
the unicellular forms are held together by a sort, of a slimy mass. Ravn ger- 
minated these spores upon beer wort but compared to the conidia they are 
slow to germinate. After an interval of five days they began to swell and 
later developed hyphae. He adds that it took fourteen days for a pycnidiospore 
to develop sufficient mycelium to be observed by the naked eye. 
PERITHECIA WITH ASCI. 
In all probability, H. teres has a perithecial form. It also appears as if 
this form should make its appearance upon sterile straw. Ravn in his publi- 
cation of 1900 believed that the sclerJlia were unripe perithecia. Diedicke from 
his work upon Bromus asper Mur. and Agropyron repens (L) Beau, came to the 
conclusion that HelmintTiosporium species are a part of the life history of a 
Pleospora species. Fritz Noack^ has proven that H. gramineum has the perfect 
form Pleospora trichostoma Wint. Noack found the sclerotia occurring upon 
barley leaves in the field. These, later developed perithecia in their interior. 
This further substantiates Ravn’s statement, previously made in this paper. 
In many, cases two perithecia would be formed. By subjecting the perithecia 
to a temperature of — 10 Degrees C. for a month, Noack succeeded in ger- 
minating the ascospores immediately, Johnson® has called attention to the fact 
that the ascogenous stage of H. gramineum occurred in Ireland in 1907. Noack’s 
work would, therefore, indicate that H. teres has a perfect stage similar to 
the one reported for H. gramineum. 
GROWTH AND TEMPERATURE RELATIONS. 
The conidia germinate quickly when placed in distilled water. Ravn caused 
increased germination by adding a small amount of beer wort. When conidia 
are transferred to any ordinary media, conidiophores and conidia develop- very 
readily. 
On examining cultures that have dried out considerably, it was found that 
the structure of the conidia had changed; there appeared to be a shrinking 
or departure of the respective divisions of the conidium from the outside wall. 
In some cases there was a wavy undulating surface imparted, while at other 
times the outline was uniform. This same apparent shrinkage was noticed 
when spores were mounted in glycerine. From all appearances no detrimental 
