THE FUNGI WHICH CAUSE PLANT DISEASE 



231 



Perithecia were found by Viala »" and by Prillieux »" on old 

 wood, long dead from such attack. These belong to the genus 

 Rosellinia and are believed to present the ascigerous form of Dema- 

 tophora necatrix. Similar claims of relationship of this fungus to 

 several other genera have 

 been made and its actual 

 position cannot be consid- 

 ered as established with 

 certainty. 



R. massinkii Sacc. 



Perithecia sparse, globose 

 or depressed, carbonous, 

 165 fi; asci cyhndric, 54 x 

 8 At; spores dark-brown, el- 

 liptic, 1-rowed, 10 x 5 jti. 



It is reported by Halsted 

 on hyacinth bulbs. 



R. bothrina B. & Br. is 

 the cause of a tea root 

 disease. 



Pseudodematophora 

 closely allied to the above 

 forms is described by Beh- 

 rens "'^ on diseased grape 

 roots. 



R. quercina Hart, is ^'o- l^S- — ^- necatrix. 4, coremium and co- 



nidia; S, perithecia extruding spores; 6, asci 

 parasitic on roots and stems and paraphyses. After Harijg, Prillieux and 



of young oaks, producing a *' 



Rhizoctonia-like mycelium, at first white, later brown. Perithecia 

 are usually abimdant. Black sclerotia the size of a pin head are 

 also present superficially. 



R. radiciperda Mas. closely allied to R. necatrix, affects a large 

 number of hosts, among them apple, pear, peach, cabbage, and 

 potato. 



An undetermined species of this genus is said to cause a cran- 

 berry disease. '^^ Shear, however, in his extensive studies of cran- 

 berry diseases, did not find it. 



R. aquila (Fr.) d. Not. injures Morus. Its conidial form is 



