PROBLEMS AND PROGRESS IN PLANT PATHOLOGY lOI 
owing to the fact that in such pure cultures environmental conditions 
can be controlled to a degree unattainable with the higher organisms. 
Brefeld's success in culturing the smuts directed attention to this 
new method in studying the fungous parasites. Although the methods 
were adapted from those of the bacteriologists their uses with fungi 
are somewhat different. With these it is not only the gain from exact 
handling in differentiating mixed infections and inoculating from pure 
cultures, but also in completing life history investigations. With 
the imperfect fungi and Pyrenomycetes the method is especially 
applicable and the recent work on Glomerella by Shear^ and Edgerton^ 
illustrates well its advantages. To this method Phytophthora infestans 
has at last yielded the clue to its complete life history,^ although here 
as always the developments in the culture tube need to be checked 
by comparison with those in nature. 
For culturing the plant pathogens the value of the solid over 
liquid media and of vegetable over animal extracts becomes increas- 
ingly evident with experience. Thus the merits of Clinton's oat agar 
which gave such important results with Phytophthora have again 
been shown by the development upon this medium in our laboratory 
of perithecia of the apple scab fungus in greater abundance and vigor 
than ever observed in nature. It should be assumed that for all 
such fungi which develop part of their fruiting stages saprophytically 
we may perfect culture media and methods which will not only simu- 
late but may improve on those of nature. 
And even the so-called, obligate parasites deserve attention, for 
we are not restricted to artificial or dead media in pure culture work. 
The living sterile tissues of the proper host may be secured for many 
parasites providing only the need is sufficient to justify the pains- 
^ Shear, C. L. and Wood, A. K. Studies of fungous parasites belonging to the 
genus Glomerella. U. S. Dept. Agr,, Bur. PI. Ind. Bui. 252. 1913. 
^ Edgerton, C. W. Plus and minus strains in an Ascomycete. Science, N. S. 
35: 151. 1912; also paper read at this Atlanta meeting. 
^ See Jones, L. R. and Giddings, N. J. Studies of the potato fungus. Science, 
N. S. 39: 271. 1909. See also, ibid. 30: 813, 1909; 31: 752, 1910. Clinton, G. P. 
Oospores of potato blight. Science, N. S. 33: 744, 191 1 ; Conn. Agr. Exp. Sta. Rept. 
1909-10: 753. Jones, Giddings and Lutman. Investigations of the potato fungus. 
U. S. Dept. Agr. Bur. PI. Ind. Bui. 245. 1912. Pethybridge, G. H. On pure 
cultures of Phytophthora infestans De Bary and the development of oospores. Sci. 
Proc. Royal Dublin Soc. 13: 556. 1913. 
See abstract of paper by F. R. Jones: "Perithecia in cultures of Venturia 
inaequalis." Phytopathology 4: 52. 1914. 
