1912] WOLF—ACTINONEMA ROSAE 227 



Germination of ascospores 



Considerable difficulty was experienced in germinating the 

 ascospores. All attempts to employ artificial" media have been 

 unsuccessful. Spores from the same preparation have been used 

 in poured and planted plates of bean agar, in hanging drops of 

 water, in similar drops in which has been placed a small piece of 



made 



and 



germination 



method. Germination occurs within 24 hours, the larger 



more often germinating, althoug 



germination. A germ tube is characteristically formed at one 

 side near the end of the spore. This hypha soon branches and 

 septa are laid down (fig. 18). Occasionally two tubes are formed 

 from a single cell. In about 35 transfers of spores to bean pods 

 made under aseptic conditions no growth was secured. From 

 these and the foregoing experiments it would seem that the asco- 

 spores are dependent on some stimulus of the living plant for 

 germination. There may be some advantage to the parasite in 

 this, since many spores would germinate before they are able to 

 reach a suitable location on the host. 



Artificial infection 



Ascospores were used in the infection experiments. Since they 

 are discharged in such masses in the opened perithecia, they can 



*d free of everything else. Several series of poured 



remo\ 



from 



sterile, which indicated that no other spores except ascospores of 

 the rose fungus had been carried over. The spore 



masses 



first removed to a drop of sterile water on a slide. With a needle, 

 then, some of the spores were transferred to drops of water on the 

 leaves of living roses. The plants were then covered with bell- 

 jars and were allowed to remain covered for two days. Infec- 

 tions from inoculations made April 27 were very evident by May 7, 

 appearing as small black areas. By May 15 mature acervuli and 

 conidia of the Actinonema type were formed, thus completing 

 the life cycle and Connecting the two forms. Inoculations were 



