K. 8. Salmon h.") 



It is cloar thiit tho HUNcoptibility hIiowu Uvrv h\ (>/i',\H wiw Htrictly 

 Im'al or U'in|x»nirv. Viirious hy|xtthoHrH may l>r julvmiccil to jwcmmt 

 for it: (I) that the i-niHlitions of growth t»Mii|H»rarily IikIiummI moiiu- 

 iimoiint of Hiiwr|»til>ility ; (2)that inm'uIatiouM when* a ^nn-at niiiiilMT of 

 conidia art' uhimI may cause at the |)la<'<> of iiionilatioii a ntrictly l«K>al 

 infcctit)!!. — JVM in the oaHos reronli»(l ot "Muh-iufectiori'"; (M) that the 

 plant OA'.'iH is ^rjulually Ihmh|; clian^^Ml in itn "conMtitution" an the 

 n*8ult «»f cultivation in manun'd ^^romul ; (4) that the conidia used in 

 this Kx|HTiment ha<l exceptional |H»werM of infection (which weakened 

 iw the mildew j;rew on the ))lant, so that the conidia pnxluced there 

 wi'rt» iinahh* to infect the plant further). The Huhject in diwuHwd 

 further at |Mi^e 8(5. 



AVyxT. 3'. Two .shoots (of e(jual hn^th and vi^'our) of two |M>tt<d 

 "cut.s" o\' ()R'\H and Z',V.) were chosen, and nn each sh«>ot 1 leaf (at the 

 3rd n<Mle from tht^ ajM'x) wjis irxK-ulatcd at three places^ The leaf in 

 each vixso was just exj)anded. Hy the IDth day the iiKK-ulated leaf of 

 Z89 bore small, di'iisely |K>wdery patches at all the inoculated places, 

 and 4 other leaves on the shoot bore each a powdery patch. No infec- 

 tion resulted on any leaf of ()Rl]H. 



Exper. 4. Two shoots (of eipial length and vigour) of a |)otted 

 "cut" of 0/^38 and of a seedling plant of the wild hop from Italy -of 

 unknown susceptibility — were chosen, and on each shoot two leav<'s (at 

 the 3rd node from the apex) were inoindat^ed at three places. On the 

 12th day the seedling plant wjis fully infcjcted at all the six places; 

 there were also, by this date, numerous powdei^ patches on seven othei- 

 leaves. No infection whatever had occurreci on OH'.IH. The same 

 results were recorded on the 21st day. 



hJjcj)€r. 5. The plants used were potted "(Mits" of 071*38, the var. 

 neo-mexicanus (Kef No. A A 9) and a ccM-tain seedling (Kef. No. ()C 32) ; 

 one leaf (at the 3nl node from the ap«!x) of a vigorous shoot, <nie foot 

 long, of ejich plant was inoculated at three jilaces. Kavh leaf was 

 copiously in<K:ulate(l with conidia taken from the sam<; sources. On the 

 7th day the plants A A !) and 0^*32 were infect<(l at the three inocu- 

 lated places on th<'ir leaves, where inimerous, densely powdtiy patches 

 (xxjurred ; other leaves on both the; plants also bore |)atclies of mildew. 

 No trace of infection lijul resulted on 0/j* 38, either on the in<»culate(l 



' Sec The Neic Pln/tohyiMt, Vol. in. p. 110 (I'.JOI). 



'•* In thiH Experiment and in all the followin;^ oneH, the conditioiiK of growth were 

 normal. 



^ In each of thcHe ExperimontH u difTeicnt potted *' cut" wuh UHtil. 



i\ 2 



