772 



Set b, twenty-eight hills planted with clean Beauty of Hebron seed; every second 

 hill uiifertilizetl, the rest fertilized with manure from a horse fed on hay and oats; 5 

 per cent seahhed in hills containing manure. 



<S'6« f, twenty-eight hills jilanted as in «e/ 6, hut every see(md hill fertilized with 

 manure from a horse fed on oats in whieh pure cultures of the scab fungus had been 

 mixed; 50 per cent scalilnd in hills ci>ntaining manure. 



Set d, fourteen hills planted as iu h, with addition of a trowelful of oxide of iron 

 in the alternate hills, every second hill fertilized with mixed fertilizer; }< per cent 

 Bca)>l)ed in hills treated with oxide of iron; 2 i»er cent scabbe<l in alternate hills. 



5p/ €', fourteen hills ]danted as in bAho alternate hills containing broken ]ilaster 

 and cement, the rest mixed fertilizer; (JO i>er cent scabl>ed in hills containing )daster, 

 etc.; 6 per cent scabbed in alternate hills. 



Set f, twenty-two hill.s, every other row planted with scabbed seed from La Fayette, 

 Indiana (unfertilized), the rest as in itet b, nnfertiliz«'d ; 50 per cent scabbed iu hills con- 

 taining La Fayette seed; 4 per cent scabbed iu alternate hills. 



Set (/, twenty-eight hills jilanted as iu b, the alternat« rows fertilized with wood 

 ashes, the rest with connnercial fertilizer; 7.5 per cent scabbed in bills containing 

 ■wo(»d ashes; 12.5 ](er cent scabbed in alternate hills. 



As far as so small an experiment is of value the results seem to show that in clean 

 laud, in whieh about fi )ier <eut only of the croi> of jiotatoes would be normally 

 Bcabbed, (1) scabbed seed very greatly increa.ses the number <d' diseased tubers )»ro- 

 dnced; (2) barnyard manure which has ncd been (outaminated by the scab fungus, 

 either by food ingested or otherwise, may not materially inerea.se the amount <ds<ab; 

 (3) oxide of iron in annmnt snlbcieiit to color new tubers red exerts no apjireeiable 

 induenceon the amount or virnleuee (dseali; (1) jilaster and cement, foi sonu* reas<ni 

 not apjiarent, exercise a very deciiled intluence, especially upmi the virulence of the 

 disea.se, which wa*s worse in the.se hills than in any others; (5) wo<id ashes have no 

 apparent connection, as has been suggested, with the ](resence of the disease. 



Although the hills fertilized with barnyard manure from a horse fed with jiure 

 culture of tin- scab fungus show a decided increase in the amount of scab, the exjieri- 

 im-ui can hardly be considered a fair one, !W the cuUun-s in question consisted almost 

 wholly of the vegetative mycelium of the fungus, so that c()mparatively few spores 

 were ingested, and the ])urcly vegetative liypha- may have been killed in the digest- 

 ive tract, such spores as were present alone surviving, and i»erhai)s multi]>lying 

 only to a limited extent in the feces after evacuation. The reverse would be true 

 where scabbed jiutatoes, on which the sjmre formation is always very abuml.inf, 

 were fed to stock, ami tin- writer is convinced that tin- jiraclice of feeding disea.sed 

 tubers in this way is one of the mosi imjiortant means by whiih llie iliscase is sprt-.id 

 ♦Ml farms. " ' * 



The condition of the hills trea<<-il with i»lasl«-r an<l cement was very striking, the 

 scabs upon tlie tubers being uniisuaHy decji and widcsiuead ami the gray aiipearanco 

 produced by the fungus very consiucuiuis. 



The jx^tato s<'ab limous is described as follows: 



(iDspora Hvabics, nov. sp.— Vegetative byi>lne brownish O.Od-l // in diiinuter. curving 

 irregularly, sejitate or pseudoseptate, branching. Aerial hyphu- at lirst w hit*', then 

 gray, evant-scenl, breaking up into ba<teria-like .segments after having juoilnced 

 single terminal sjiiral sjnues ( f) by the coiling of tlnir free extremities. Forming a 

 lirni lichenoid iielliele on nutrient Jelly and usually proilncing a bla« kish brown dis- 

 c<doratiou of the substratum on whieh it grows, causing the disease know n as •• -. ab" 

 on potato tnbersand a .similar disease of beet roots (sec. llolley). 



The Inngiis is referred to Oospoia merely for the reason that it appears more nearly 

 allied to c.Tt.iin forms included in this genus by Saccardo than any others known to 

 the writer. There seems to bo. however, at leastom^ and perhajis several sai>rophytic 

 forms, having the sanu- morphological characters. \\hi<h may prove constant enough 

 to warrant anew generic designatiou. 



