ASCOMYCETES 



239 



neck is lined with periphyses. The perithecia are seated upon 

 a slight subiculum. 



The wall of the perithecium at maturity is made up of paren- 

 chymatous cells more or less polyhedral in form. The asci are 

 cylindrical in the spore-bearing portion and measure often 100- 

 130X 11-14/U. Each ascus contains eight spherical ascospores, 

 the latter are brown in color and show at maturity a wrinkled 

 exospore or surface. Paraphyses of somewhat peculiar form are 

 present. These consist of a loose chain of large cells, as shown 

 in Fig. 100, b. The development of the perithecium, apparently, 

 has not been studied in detail. 



Control. It is believed that it will not be possible to control 

 such wilt diseases by the use of any toxic substances in the soil. 

 Prevention is therefore dependent upon the choice or develop- 

 ment of varieties which may be more or less resistant to this 

 fungus, as already suggested. Moreover, it will probably be neces- 

 sary to look toward the selection of varieties locally resistant, since 

 the relation of such varieties to climatic and soil conditions seems 

 unquestionably to affect resistance to this fungus. 



Other wilt diseases. Wilt diseases of various other plants have 

 been studied and some have been referred provisionally to the spe- 

 cies of fungus above described, such diseases, for instance, as the 

 stem disease of ginseng, the wilt of the flax, wilt of okra, etc. There 

 are, moreover, other fungous diseases due to species of Fusarium 

 which may or may not be conidial stages of some species of Neo- 

 cosmospora. Examples of such diseases are to be found in the stem 

 blight and dry rot of potatoes, caused by Fusarium oxysporum. 



XXXIII. A CANKER OF WOODY PLANTS 

 Nectria cinnabarina (Tode) Fr. 



Durand, E. J. A Disease of Currant Canes. Cornell Univ. Agl. Exp. Sta. 



125: 23-38. figs.1-16. 1897. 

 Mayr, H. Ueber den Parasitismus von Nectria cinnabarina. Unters. a. d. 



forst-bot. Institut zu Miinchen 3 : 1-16. pi. 1. 1883. 

 Wehmer, C. Zum Parasitismus von Nectria cinnabarina Fr. Zeitsch. f. Pflan- 



zenkr. 4: 74-84; Ibid. 5: 268-276. pi. 2. 1894. 



Several important fungous diseases are attributed to different 

 species of the genus Nectria. Perhaps the two most destructive 



