194 MAINE AGRICULTURAL EXPERIMENT STATION. I909. 



four-celled spores which do not differ from the spores devel- 

 oped under natural conditions. On potato agar in petri dishes, 

 the spores are four celled but vary in size. On prune agar, 

 bean agar, and in prune decoction, the spores vary in size and 

 number of cells as shown in Figs. 31 and 32, all gradations can 

 be easily found from typical four celled spores of the size found 

 under natural conditions to those having as many as nine cells 

 and measuring 9 x 43 microns. 



In prune decoction, the fungus grows rapidly and when the 

 cultures were 5 days- old a thick pellicle was formed over the 

 surface of the liquid and large numbers of spores were being 

 produced. On sterilized apple twigs, the fungus grows well 

 forming a considerable amount of serial mycelium which is 

 brownish gray in color, some of the large hyphse being deep 

 brown in color. The mycelium also grows in the liquid at the 

 bottom of. the tube. Spores are produced in black masses on 

 the wood. AMien the spores are mature, they are mostly 

 broken off from the stalks on which they are borne, but in some 

 cases they were found still attached and the stalks measured 

 18-22 microns, in length. On sterilized bean pods, potato, 

 carrot, and turnip cylinders, there is a considerable develop- 

 ment of serial mycelium which is light colored in young cultures 

 but becomes dark in old cultures. Part of the spores exam- 

 ined from turnip and carrot cultures were very abnormal, the 

 cells being large and rounded and in some cases separated 

 resembling the conditions seen in germinating spores. 



Smith (5) has made a study of the cultural characters of 

 Coryneuni beyerinckii Oudem. He found that spores of that 

 species taken from the bark or from leaves did not grow readily 

 in plate cultures and that made it somewhat more difficult to 

 isolate the fungus in pure culture, but after colonies were 

 obtained, the fungus grew very well producing a little mycelium 

 and thick black crusts of spores on prune agar. This differs 

 from C. foliicohim in which spores taken from old cankers in 

 the spring before the leaves open germinate in considerable 

 numbers when sown in petri dish dilution cultures in prune 

 agar or in bean agar. When such spores were placed in hanging 

 drops of prune decoction, about one-half had germinated at 

 the end of 18 hours at room temperature. 



