NECTRIA. 



18/ 



grown over in course of^ time by the activity of neighbour- 

 ing living tissues, but the rapid development of the mycelium 

 of this Ncctria prevents any sucli healing, and brings about 

 death of more liark. As a result the so-called " cankers " are 



<m-^-t 



Fio. Sl.—Kectriu .^^-..; i aiikeron H;izcl. ' 



place of infection, a partially broken branch-fork. 



Fio. so.— .Vtcfivc i'i7;.<.,;,„... ( 'anker 

 ou a stem of Beech, (v. Tubeuf 

 phot.) 



produced. The mycelium at first gives off tiny unicellular 

 conidia on the bark, then later white cushions bearing fine 

 conidiophores, from which are abjointed multicellular conidia, 

 shaped like a sickle. Infection is brought about by the 

 germination of spores or conidia on wounded parts of the 



