240 



FUNGOUS DISEASES OF PLANTS 



of these Nectrias are Nectria cinnabarina (Tode) Fr. and Nectria 

 ditissima Tul. Both of these fungi seem to follow other injuries, 

 but either may, after gaining a foothold, spread rapidly from plant 

 to plant and be of the nature of an epidemic. 



Distribution. Nectria cinnabarina is very 

 commonly distributed throughout temperate 

 regions, at least, and may be found growing 

 upon a great variety of hosts. It has been de- 

 scribed as the probable cause of an occasion- 

 ally destructive disease of currant canes, and 

 in the same state it unquestionably exists as 

 a parasite upon the pear. The horse-chestnut, 

 the china berry, and other trees in various parts 

 of the country frequently show the effects of 

 its injuries. Durand submits evidence to the 

 effect that it is a more or less destructive dis- 

 ease to currants throughout New York, 1 and 

 it has been mentioned as a currant disease in 

 other sections of the country, causing affected 

 parts to dry up and eventually die. In Europe 

 it is also known to cause disease in several 

 hosts, all deciduous trees. 



The fungus. The disease seems to infest 

 particularly the cambium and soft bast. It is 

 therefore unlike its relative Neocosmospora, 

 and would seem to be more or less localized, 

 gaining entrance, as previously stated, through 

 wound areas, and probably killing the twig or 

 cane so soon as the latter is girdled. The 

 hyphae are closely septate, and large stromatic 

 areas are produced upon the epidermis or within the cortex 

 (Fig. 102). These rupture the surface layer and appear as tuber- 

 culiform stromata, crowned with minute, short, erect, or flexuous 

 conidiophores which bear simple, ovate conidia. The general 

 appearance of this stroma superficially is that of a pinkish disk. 

 The conidial stage appears usually during the summer, and it is 



1 This fungus is certainly not responsible for the common currant cane disease 

 of eastern New York. The latter, which is typically a wilt, is discussed later. 



Fig. ioi. Nectria on 

 Currant. (Photo- 

 graph by E. J. Durand) 



