34 MASS. EXPERIMENT STATION BULLETIN 183. 



(e) Insects, centipedes and worms carry the spores, as has been proved 

 in the laboratory by permitting them to pass over sterile plates after 

 being on dead twigs bearing spores. (/) The water used in watering the 

 plants is usually driven from the nozzle with enough force to splash spores 

 and bits of mj^celium from the soil or debris on the ground up to the 

 stems. Probably most of the stomatal infections above ground are 

 started in this way. 



The spores of many fungi are so light that they float around in the 

 air and are wafted about by very light air currents. It does not seem 

 likely that the spores of Cylindrocladium are carried about to any great 

 extent in this way. They are bound together in solid heads of spores, 

 which are probably too heavy for currents of air such as usually occur 

 in rose houses. That they can be dislodged and blown some distance 

 by strong air currents was proved in the laboratory by passing a strong 

 current of air from a fan over spores growing on a dead rose stem, and 

 exposing agar plates 1, 2 and 3 feet away. Colonies of the fungus devel- 

 oped on all of them, but it is hardly probal^le that so strong an air current 

 would normall}^ occur in rose houses. They could also be blown about 

 on dust particles, but the soil in rose houses is rarely permitted to become 

 dry enough to form dust. 



OCCURRENCE OF TWO SPECIES OF CYLINDROCLADIUM 



ON ROSES. 



During these investigations a second species of Cylindrocladium has 

 frequently been isolated. It was first taken from the roots of a plant 

 which had typical cankers on the crown. Later it was secured a number 

 of times from crowns and from dead areas of the plant above the ground. 

 It was commonly isolated directly from the soil in the rose beds, from 

 the surface to S inches down. Except for its size, it resembles C. scoparium 

 so closely that the writer was at first inclined to consider it but a dwarf 

 variety of that species. The spores are only about one-third as large 

 as those of C. scoparium. Although numerous isolations have been 

 made, no transition forms between the two have been found. The small 

 form has been grown through many generations in culture, and has 

 remained constant on all media. 



Infection experiments were carried out, but all attempts to produce 

 the disease by the same inoculation methods as were used for the larger 

 form gave only negative results. The fungus grows and produces spores 

 on the dead tissue about wounds and on cut stubs, but seems to lack 

 ability to spread to healthy tissue. The small form then appears to be a 

 saprophyte, while the larger one is a parasite. 



In order to determine whether there are cultural differences by which 

 they could easily be distinguished, the two forms were grown simul- 

 taneously on five standard culture media. They show very marked 

 diagnostic differences. Such differences in morphology, pathogenicity 



