NATURAL AND ARTIFICIAL INFKcTIoN. 53 



the stomata. Also, whether the germ-tube formed from a 

 germinating spore penetrates direct, or if, as shown by I)..- I'.arv 

 for SclerotinKi, a niyceliuni vigorous enough to penetrate must 

 h'rst be developed sapropbytically. 



In this connection 1).- l',ary ' states that the ^erm-tulies fr..iu all aeeidio- 

 s]M)ivsainl liredospores only penetrate 1>\ stomat.-i. ami thence extend through 

 the intercellular spaces. Kntry through the stomata ha-; also lieeii ol,-ci \ ,-d 

 on the i^erm-tulies from sporidia of Leptopin-i-inin ////////,/, and from spoi. 

 Hi'ti/h,,,,'!. On the other hand, -.M m-tubes from the spores of teleuto-poi .->. 

 from -pores of Peronosporeae, Ustila^ineae, >'</</-///'//, /'<-///.<//<////, /',-,,- 



(<>iiii/i:i'.t, and Si/in-l,i/triniu etlect an entrance thinu-li the oiil.-r c,-H-\valls int<i 

 the epidermal cells <>r stoinatal ^uard-cells. he r>arv also descn]ie> the 

 jieculiar behaviour of zoospores of (',/*?,,/,,!.< and Peronospora timbelliferarnm, 

 \vhich, if they come to rest near a st^ma, jerniinatc, and the ^ei'in-tulie 

 enters therein, whereas one developed in water soon dies. Certain fmc_ r i 

 penetrate sometimes through the membrane, sometimes Kv a stoma. '.(/. 

 Pkytophthora //>/<.^< '//.-,, /'./'(//">/</-./ parasitica, !'..< /</.>/'- //-'/ vaccinii. 



In the case of Phytophthora ///">//, Hartig found that the ^erm-tubes 

 from the xoospoies crejit aloiiLT the surface of tin- leaf till they reached a 

 place where two epidermal cells adjoined ; there they entered, and only 

 rarely -TOW into the epidermal cells. The ,'erm-tulies of /',/<//(//./ ..< macro- 

 and T'ib"i-<-ii'i'i tri'-ntnli.t enter their In^t- in the >am>- wav. 



From experiments, one is able to determine the conditions 



nurable, or otherwise, ti. inl'ci-timi by parasitic fiuioi: to ascertain 

 influence of temperatuiv, air-moistuiv, watcr-coutfiii .if tlie 

 host, hairiness of the leav.-, and the etlect <>!' ivsin or other 

 excretions as protections t. \\dunds. K,,r example, it \vas in 

 this way that. Hartig found SnJi.i- j>iil,-l,,-<i (pruinosa x daphnoides) 

 to bt- a hybrid which, on account of its hairy leaves, is more 

 n-H-tant to M,lnini>xui;i than ."w //',/ y//v//'//</.sv/.- Much iu\'cst j._;a- 

 tioii remains yet to be dom- in this direction to ascertain what 

 varieties or species of cultivated plants aiv likely to be least 

 liable to attack by epidemic diseases. 3 



The methods used in carrying out aititiejal infection are 



ed on the observation uf cases of natural infection. MM-I 

 frequently infection is peifoinied by means of spore-. lr-s ..fi.-n 

 \\ith mycelium. 



The spores of lower Inrnis of funui are Lienerallv distributed 

 oy means of water, e-preially in de\v or rain. /oospmcs aic 



1 . 1/- ./-/.A., /i, : /i/ ii,n/ /,'/'o/.../// (./' ///. /';i//.//, l-lniriisii I'Mii ji,ii. p|> :>iii :,i; - j 

 Haiti-, Duetuet ".>' Trees, Kn-li-li Ivlitimi, ISMI, p. 171. 



3( < 'li:i|>ti-r \'. mi " 



