258 



Rosellinia aquila (Fr.) De Not. This species attacks many kinds of 

 trees but is probably best known for its activity on mulberry roots. As 

 a rule the trees are killed by the dense mycelium enveloping the roots. 

 The mycelium penetrates every part of the root and is especially abundant 

 in the medullary rays. When the host is quite dead the dark brown 

 perithecia are found crowded together on the brownish velvety patches 

 that previously bore the cOnidia. The conidial form of this species is 

 known as Trichosporium fuscum. This is one of our most common species, 

 and a description is found elsewhere in this paper. 



Rosellinia necatrix (Hart.) Berl. This fungus produces a disease 

 known as the "white root rot." This species is, however, rather rare in 

 this country. One of the peculiar characteristics of the disease is its 

 power of attacking practically every plant with which it comes in contact. 

 It is especially disastrous in vineyards, orchards, etc. Some of its more 

 common victims are vines, fruit trees, oaks, maples, beeches, pines, beans, 

 potatoes and beets. 



The mycelium of this fungus travels underground and attacks the 

 rootlets, killing them and gradually working its way up to the larger roots 

 and from them to the body of the plant proper. Here in some instances 

 it breaks through the cortex as a white fluffy mass of mycelium. Sclerotia 

 are formed on the exposed parts of the infected roots, which give rise to 

 dark, bristle-like conidiophores which bear numerous conidia at their 

 tips. Globose swellings on the exposed portions of the mycelium are 

 sometimes formed, which, according to Viala, are capable of emitting 

 mycelium which forms a new plant. The ascigerous stage has been dis- 

 covered by Viala, appearing only on trees that are well decayed. 



Rosellinia radiciperda Mass. This is the cause of the disease known 

 as the "New Zealand write root rot" and is very closely allied to the 

 fungus causing the "white root rot" of Europe, R. necatrix. It attacks the 

 roots of the apple, peach, pear, etc., and also such plants as docks, ferns, 

 sorrel, cabbage and potatoes. Sometimes the trees are killed here and 

 there, but often whole areas are swept away. 



The white filamentous mycelium attacks the roots and the bark just 

 under the ground. This eventually gives rise to sclerotia which later 

 produce the conidial stage. Next the mycelium becomes dark colored and 

 gives origin to the black globose pycnidia containing stylophores. The 

 ascigerous stage is found on dead tree trunks and stumps that have been 

 dead for considerable length of time. 



