546 SPECIAL PLANT PATHOLOGY 



parts of the cell wall, and the parts of the springwood fall apart readily, 

 because of their porous character. The fruiting bodies of this fungus 

 are extremely variable depending upon the kind of wood on which they 

 grow. The sessile sporophores may grow singly, or, more usually, 

 many of them together, forming a series of closely overlapping brackets. 

 They are readily recognized by the soft, hairy upper surface with bands 

 of white and yellow color, although these colors are variable. The 

 young sporophores are fleshy, but become leathery with age. Their 

 lower surface is white and the pores are minute and regular. Treat- 

 ment of the wood with chemic preservatives has been found efficacious 

 in preventing the attack of such fungi as Polystidus versicolor, and 

 most of our large railroads have machinery where the steeping of 

 the ties in chemic preservatives can be accomplished quickly and 

 inexpensively. 



Rye (Secale cerale, L.) 



Ergot (Claviceps purpurea, Tul.) (Figs. 56 and 57), — The ergot fun- 

 gus is found on rye both in America and Europe, where during wet 

 warm weather it may be extremely prevalent. It gains entrance to the 

 host at the base of the young ovary penetrating the ovary wall and 

 gradually replacing the tissues of the rye ovary. This is accompanied 

 by an enlargement of the ovary which at its upper end presents a some- 

 what spongy character. This is due to the outgrowth of the mycelium 

 in the form of twisted strands, the marginal hyphas of which acting 

 as conidiophores abstrict off conidiospores. This early stage was 

 known as the Sphacelia stage. Later, as the time for the maturing of 

 the healthy grains arrives the diseased ovaries will be found to be re- 

 placed by bluish-black horn-like bodies which project conspicuously 

 from between the glumes of the rye spikelet. The rye ovary is re- 

 placed by a hard body with a blackish surface and white interior 

 known as the sclerotium. The ergot spurs, or sclerotia, perennate as 

 such until the following spring, when they send up one or several 

 outgrowths, or stroma, with a knob-like end of a yellowish-brown color. 

 In the hyphal tissue, which comprises the knob-like portion of the 

 stroma, fiask-shaped perithecia are formed with short necks and 

 slightly protruding ostioles. The asci contained in these perithecia 

 are elongated and contain eight needle-shaped ascospores, which 

 measure 60 to 70/i in length, and issue from the tip of the ascus by 



