84 ReHiHtance to Mildew in Hops 



where the experiment was carried out. In tho case of this and of all 

 the experiments described below in order to make the inoculation 

 material hh unifoim .is possible (or nil the plants in each experiment, 

 the conidia lakcn lioin ('.irli " iiovvdcry" patch wore distributed equally 

 as far as posHil)l(! on all Mic |)lniil;8 in the process of inoculation. The 

 drops of water w(jro found to have cvapoinlcd in a f(^w hours' time. 



By the Slst day after inoculaUon the leal" of Z^A was infected at 

 the three inoculated places, wlicro clusters of conidiophores occurred. 

 ,Nine days later these p.itdK s h.id become "powdery" with conidia, and 

 patches of mildew wciv .ilso pivsent on four other leaves and at four 

 places on the stem. No Uww of any infootion resulted on 0-R39. The 

 two plants stood side by side, and thus exposed to the same chances of 

 inoculjition from Hurroundim^ inildcucoxcicd pl.mls. Tii this cxpcrimont 

 the inuiHually prolonged " inciiU.ithui jM'iiod of the mildew \v;is doubt- 

 less due to the very abnormal weather conditions of the period (March, 

 11)1 7) when rapid elianj^^'s of teniperatiii-e oeeiiiiiMl. Under thiise 

 conditions the shoots of both plants made scarcely any growth, and the 

 l(>aves showed a slight injury round th<"ir maiL;iiis which turned brown. 

 riuler Mi( se a(lveis(^ couditions of gi-owth the immunity of OJ? 39 

 remained uiiclianged. 



Exper, 2. One leaf of a potted "cut" of 0/^ 38, and one leaf of a 

 similar potted " cut " of another seedling (Uef No. Z39) of the wild hop 

 from Italy were inoculated as in Eayper. 1. By the 31 at day the leaf of 

 Z89 bore small patches of mildew with weak clusters of conidiophores 

 at the three inoculated places ; tho leaf of OR 38 bore similar patches 

 of mildew at two of the three inoculated places. Nine days later the 

 inoculated loaf of Z 39 still bore weak sub-powdery patches at the three 

 places, but the leaf was now beginning to die ; on the leaf of OR 38 the 

 weak clusters of conidiophores — scarcely more than " sub-infection " — 

 were still visible at the two places. At the end of the Experiment — 

 58 days from the inoeidation — the inoculated leaf of Z39 had withered 

 up, and nil tlu leax. s ot th(^ original shoot (which had scarcely elongated 

 under the ahnormal w ( i i h . i conditions noted in Ewper. 1) were brown 

 at I heir ed^cs; a new basal shoot bore loaves with numerous patches of 

 niildtw (.11 them. With regard to Oli*AH, the original shoot, which had 

 rcMnaiiied chi>cki>(l in growth for some time, had now elongated and was 

 two feet long; the!(> was no trace of any mildew on the inoculated leaf, 

 nor elsewhere^ on l\\r numerous h>avi>s, although all the leaves were now 

 exposed to IVeijnent inoeulations from adjacent mildew-COvered plants. 



