1 68 Journal of Agricultural Research voi. x, No. 4 



indistinct zonation, entire or slightly lobed margins, and produce 

 pigment only with age or not at all. Colonies of Xylaria sp. enlarge 

 much more slowly than those of the two other species. The zonation 

 of colonies of X. hypoxylon results from the formation of aerial myce- 

 lium at the growing margins followed by appressed mycelium. The 

 pigment, which is at first greenish and becomes almost black with age, 

 forms first in the central zone and appears in the other zones success- 

 ively from the center outwards. The upright stromata begin to form 

 when the colonies are about 2 weeks old and may appear at the center 

 or on the margins of the zones. They vary in numbers from 2 or 3 

 to 20 or more. The stromata of X. hypoxlon are borne singly or in 

 groups and may become 4 cm. or more in length, with a diameter of 

 2 or 3 mm. (PI. 17, E). Conidia are produced at the upper extremi- 

 ties in four or five weeks. Cultures of X. polymorpha and Xylaria sp. 

 have commonly produced only rudimentary stromata. One culture of 

 X. polymorpha has, however, developed stromata 5 cm. long and 2 mm. 

 broad. Gueguen's (7) experience that the development of X. poly- 

 morpha in culture is corr^ated with its seasonal development in nature 

 is of interest in this connection. A more detailed study of the produc- 

 tion of stromata and conidia is reserved for a later publication, 



PATHOGENICITY OF THE XYLARIAS 



Little is known of the exact mode of life of the Xylarias in nature. It 

 has probably been assumed very generally that they exist as saprophytes; 

 and the appearance of their fructifications on stumps, fence posts, and 

 similar situations is evidence that they are commonly saprophytic. We 

 have found but one reference which bears on the question of parasitism. 

 Harder (8) obtained evidence of the pathogenicity of X. hypoxylon when 

 inoculated into small wounds in short pieces of living i -year-old shoots 

 of two trees (the species were not named). After three months in moist 

 chambers the shoots were still living, as shown by the development of 

 buds and roots, the bark at the point of inoculation was browned to a 

 distance of 3.5 cm., and the wood beneath was brown and dead. The 

 inoculum was recovered. 



Our inoculations were made on living apple roots and branches in 

 moist chambers and in the field, also on roots of peach {Amygdahis per- 

 sica), hawthorn {Crataegus spathulata), red oak (Quercus rubra), white 

 oak {Q. alba), and walnut {Juglans nigra) in moist chambers. 



MOIST-CHAMBER INOCULATIONS 



Pieces of roots or branches about 6 inches long and i inch in diameter 

 were used. After a preliminary washing and sterilization in alcohol a 

 small notch was cut with a sterile knife and the inoculum of mycelium 

 from the growing margin of a colony introduced. Moisture was main- 



