2 8o FUNGOUS DISEASES OF PLANTS 



cell. The various spore forms of this fungus have yielded in cul- 

 ture a perfectly similar mycelium, and infection experiments seem 

 to leave no doubt as to the genetic relationship. 



Control. Preventive measures might at least apply to nursery 

 stock and to young trees recently set. It may be supposed that 

 thorough applications of the 5-5-50 Bordeaux very early in the 

 season would greatly assist in the control of this disease. 



XLVII. A DISEASE OF YOUNG OAKS 



Rosellinia Quercina Hartig 



Hartig, Robt. Die Eichenwurzeltodter. Unters. a. d. forst.-bot. Inst. Miin- 

 chen(i88o): 1-32. pis. 1,2. 



This fungus occurs as a parasite of seedlings and young oak 

 trees in Germany. 1 It affects primarily the roots and the basal 

 portion of the stem. It has been prevalent in northwestern 

 Germany and particularly disastrous when it occurs in the seed 

 beds. The greater amount of injury results to seedlings from one 

 to three years old. The effects of the fungus are manifest by an 

 unhealthy, pale color of the foliage, followed by withering and 

 wilting of the leaves. Young shoots, and subsequently the older 

 leaves, also wither and die. About the roots and sometimes the 

 lower portion of the stem will be found a felt-like mycelium of 

 interwoven brown threads, or strand-like aggregations. 



The perithecia are commonly produced in quantity, particularly 

 after the death of the plant. They are spherical or ovate in form, 

 and brittle in texture, with a papillate ostiolum. The asci are long- 

 cylindrical, each containing eight elliptical or somewhat fusiform, 

 brown or brown-black spores, which are ordinarily vacuolate, and 

 measure 28 X 6— 7 p. 



1 One or two other species of Rosellinia have been described as important 

 from the disease point of view. Prillieux (Comp. Rend. 135 : 275. 1902) found 

 a form on the roots of fruit trees accompanying Dematophora, which he considers 

 to be the perfect stage of the latter. He believed that the perithecia were developed 

 on the stroma on which arose the conidiophores. The perithecia measure 1.5 mm. 

 in diameter, are gray-brown in color, with a definite and darker papilla. The body 

 is composed of three wall layers, — the outer indurated and brown, the central 

 white, and the inner yellowish in color. From the latter arise the stalked asci, 

 365-380 X 8.5—9^, and small slender paraphyses. The spores long remain color- 

 less, but are finally black with small vacuoles. 



