140 INTERNATIONAL CONGRESS OF VITICULTURE 



ice may be germinated after sixty days if optimum conditions be afforded. 

 In warm, dry air they perish in five days. 



The writer has germinated conidia which have been kept for two weeks 

 at a temperature of 10 C., while those kept in a moist chamber at room 

 temperature lost their vitality in from seven to ten days. It seems safe 

 to assume that the conidia will retain their vitality in nature about a week. 



The season makes no apparent difference in the germinative power of 

 the conidia. As good germination has been obtained in October from conidia 

 collected on wild vines as during the summer. 



The germination of the conidia has been described by the writer (1913) 

 but will be rewritten at this time in order that changes in certain details 

 may be more intelligibly indicated. "At first the protoplasm is finely 

 granular but about an hour after being placed in water there appear lighter 

 hyaline spots in the protoplasm, which at the same time becomes a little 

 denser and more granular." When stained with methylene blue it will readily 

 be seen that the "hyaline spots" are the nuclei. "This continues until there 

 is a dense granular mass with clear, distinct spots arranged at regular 

 intervals. In a short time there appear in the protoplasm dark lines which 

 mark out portions about each nucleus. These lines become more and more 

 distinct and finally there are slight indentations along the margin of the 

 previously smooth protoplasm. The content of the conidium is now very 

 rough and irregular. By focusing, the individual swarmspores can be made 

 out. In a few minutes the spores break apart and become distinct bodies. 

 out until the opening becomes maximum in size when the entire mass of 

 At this point there is a pause during which it seems that the spores must 

 burst forth immediately and, coincidently, there seems to be a slight move- 

 ment among them. Suddenly through the tip of the conidium there appears 

 a bit of protoplasm of one of the swarmspores which slowly forces its way 

 spores, jerkily but rapidly, slips out.- tt is quite certain that the opening 

 is at the papilla, and is probably brought about by the dissolution of the 

 wall at this point and not by its breaking, since no remnant of the wall 

 can be found after evacuation." Istvanffi (1913) claims that the papilla is a 

 cap-like structure which is pushed off when the zoospores emerge. The 

 writer watched this process very closely and has fixed and stained conidia 

 in all stages of germination but has never seen anything which might pos- 

 sibly be interpreted in this way. 



During the preliminary stages of germination the conidium swells 

 slightly, as Farlow (1876) has already intimated, probably due to the imbibi- 

 tion of water. Ordinarily the increase in size is about 1/t in both length 

 and breadth. After the evacuation of the zoospores the size decreases about 

 2fi, becoming much smaller than the original conidium. Ultimately the 

 conidial wall becomes greatly wrinkled and shriveled. 



"The swarmspores remain for an instant at the end of the conidium 

 and then pull apart and swim away." In this connection Farlow states, 

 "They passed out rather slowly, usually one at a time, and paused for a 

 moment in front of the opening, where they remained as if not yet quite 

 free from one another. In a short time each segment began to extricate 

 itself from the common mass, moved more and more actively, and finally 

 darted off with great rapidity a full-fledged zoospore, furnished with two cilia." 

 The writer states further, "It is quite probable that the flagella are formed 



