DISPOSITION OF PLANTS TO DIsKAK. 59 



Hartig l also found that Agaricus melleus, in penetrating into 

 stools of oak, only killed those cells \\hich, as it were, rested, 

 whereas the cells of parts in communication with stool--hoots 

 are not attacked. Likewise, Schwarz states that the mycelium 

 of O ""////////// <il<'nt'is only extends through pine-shoots at a time 

 when there is little vegetative activity. 



Accidental disposition depends largely on the nature of the 

 epidermis enclosing plant-organs. The stems of many plants are 

 protected from intruding fungi from the time the epidermis i< 

 replaced by a corky layer, still better after a bark is formed. 

 Hence young shoots are in a condition of greater disposition 

 than older ones. There are, however, various grades of dis- 

 position to be observed, even when a simple epidermis forms 

 the only covering, as is the case with most leaves, flowers, and 

 many fruits. The newly-formed epidermis is, as a rule, mo>t 

 disposed while its walls are still delicate and uncuticularized, 

 hence many organs are exposed to attacks of fungi only in their 

 youngest condition. It is easy to infect and kill young leave-, 

 ami shoots of conifers with 7,W /////* /A^/A/.s/V, whereas older 

 aeedles will remain quite unharmed. Similarly with Chrysomyxa 

 rln.ilixli nili-i on spruce-needle.-. r^///y//n.^/ (( /v/ Goeppertiana on 

 silver fir, and others. Flowers are also more ea.-ily infected 

 in the yonn- stage, e.g. cones of spruce by Aeddium >/v// /'//'///'///. 



1 Hiring eaily youth plants are insulliciently protected trim 

 great cold and drought, and also from infection by paiasitic 

 fun^i. This may be because the young non-cuticularized \\alls 

 oiler le>s resistance to the germ-tubes and hau>toiia. or because 



they are more peimeable to any feinieiit excreted by the fun-us. 



Oigans developed late in the vegetative season re-emble those 

 in the >prin;_:-condition in that they have not as yet manned. 

 and are but poorly protected again>t extnmes of temperatnie, 

 or attacks of j.arasite-. 



The eondition of di>josition may le easily jironmted tur 

 purposes of artificial infection, by eidt i\ atin- the lio>t-plant - in 

 a moi>! chamber, or Ulidel' a bell-jar. The same eondition 

 mav ea>ily aii.-e in glass hon.-r> or hot-beds, hence one has. by 

 mean- of constant ventilation, to gnai'd a-ain.-! it. 



Many diseases of -eedlings (-.//. /'/ii//<>j>/i//i,'i-n omnirora, 



and /'//////'/'///) are only to be feared >o lon^ a- the stem- . !' 



1 Forttl.-naturwit / 1,,-i/f, 



