IO Journal of Agricultural Research voi.xx, No. i 



On seedlings. — When a wilted seedling is pulled out and portions of its 

 partly decayed kernel or of the young stem are examined under the 

 microscope, a great number of normally developed conidia can fre- 

 quently be seen. In rare cases masses of conidia are also formed on the 

 rotted stem above the ground. The number of conidia so formed will 

 be still greater if any particles of organic matter like straw, old stems, or 

 stubble happen to be near the wilted or heavily infected plant, since the 

 conidia-forming growth will extend over them. This growth soon dis- 

 appears, however, leaving no evidence of its existence. 



On nodes and bases. — Formation of conidia on the infected nodes or 

 bases of mature plants, while common, is never very abundant because 

 of the rapid drying out of these parts. 



On heads. — The formation of conidia on the heads of cereal crops, 

 especially of wheat and rye, shortly after infection takes place is common 

 and so abundant as to give them a very distinct pinkish or salmon 

 color. In dry weather the formation of conidia is restricted to the area 

 where the infection originally took place, this being usually the base of 

 the spikelet where the rain drops collect and the moisture is held for a 

 longer time than on any other part of .the plant, except possibly in the 

 sheaths. The spore formation under such conditions extends up the 

 several furrows formed by the joining of inner and outer glumes and to 

 some extent even between the glumes. In moist weather the conidia are 

 formed in great abundance over the entire surface of the tissue through 

 which the hyphae of the parasite extend. The latter send out conidio- 

 phores through the stomatal openings, forming at first small balls of 

 conidiophores and conidia over each stoma. Soon these balls converge 

 into a uniform layer (pionnotes) of conidia extending over a large por- 

 tion of the head. The following observation in the field corroborates 

 this fact. 



Before June 29, 191 8, the weather was dry and there were very few 

 conidia formed on the infected rye heads in the University experimental 

 plots. The last two days of the same month were rainy and compara- 

 tively cooler. Following this, conidia were formed in such abundance 

 that all the infected spikelets were practically covered with a layer of 

 conidia which gave them a distinctly pink or salmon color. 



Dry, blighted rye, wheat, or barley heads without any conidia also 

 produced conidia in abundance when placed on the ground under a screen 

 and kept moist. 



On dead organic matter. — Old straw and pieces of stems and corn- 

 stalks in fields where the year before the crop had been heavily infected 

 with the disease were often found to show large pinkish areas bearing 

 numerous conidia, some of which belonged to some of the species of 

 Fusarium which were found parasitizing wheat and corn. This condi- 

 tion was especially common on cornstalks and wheat heads left in the 

 field from the previous year and bearing the perithecia of Gibberella 



