PEACH SCAB AND ITS CONTROL. 19 



The spores were placed in drops of sterile distilled water, meteoric 

 water, aiid nutritive solutions, respectively, on glass slides in moist 

 chambers; in liquid and solid media in Van Tieghem ceUs; and in 

 plate cultures of agar infusions. The cultures were incubated under 

 various regulated conditions. The glassware was cleaned in the 

 standard manner for physiological experiments, and distiUed water 

 was redistilled from Jena glass. For most purposes, the open drop 

 cultures on glass sHdes in Petri dishes were most convenient and 

 satisfactory. 



GERMINATION IN WATER. 



In diffuse light or in darkness, at 18° to 27° C, the first evidences 

 of the germination of conidia in sterile distilled water appear, after 

 about 8 to 12 hours, as small, highly refractive, hyaline protuberances 

 of the inner walls of the spores. These gradually develop into delicate, 

 hyaline, septate germ tubes, 2 to 4 /z in diameter, which usually 

 attain a length of about 10 to 20 ix within 24 hours after the beginning 

 of the experiment. Little growth occurs after the second day, when 

 the tubes are usually 30 to 60 ix long. They rarely become longer 

 than 75 /x unless suitable nutritive material is added. The germ tubes 

 may extend from any part of the surface of the spore, but ordinarily 

 they are developed at or near the ends. If only one is produced, it is 

 generally borne at or near the basal end. Frequently a tube is 

 developed from each end, but rarely are more than two produced 

 from a single spore in pure water. 



In parallel experiments with sterile distilled water and meteoric 

 water no noteworthy differences in results were observed. 



GERMINATION IN NUTRIENT MEDIA. 



In drops of 1 per cent prune or raisin decoction, or a variety of 

 other similar nutrient solutions, the early development of germination 

 is practically indistinguishable from that in water, the effects of the 

 nutrient media being manifested chiefly in the rapidity and vigor 

 of development. In such solutions, under the conditions already 

 mentioned, early stages of germination may be observed within 

 4 to 8 hours. After 12 hours the germ tubes usually measure about 

 3 to 4 by 15 to 25 p.. Within two days they frequently attain a 

 length of 150 to 250 ix and become considerably thickened, branched, 

 and septate. 



In sap expressed from green Elberta peaches germination is practi- 

 cally indistinguishable from that in 1 per cent prune decoction. 



In plates of 1 per cent prune agar, or a variety of similar agar 

 infusions, germination closely parallels that in drops of prune decoc- 

 tion. 



In Van Tieghem cells the spores germinate normally in various 

 liquid and solid media. 



