W. A. (IIITIIN. 



TIIK l)i;\i;i.(ll'\iKNT ()|- DISKASK RKSISTA.M VAItIKTIl'S OK l'LANÏS. 



lailrd lo (>(|iiol tliose already menlionetl. Followiiija; Ihe success ol' Hie Rivrrs 

 colloii. slill ollier varielies hâve bcen indepeiidcnlly developed ])y Ihe planlers. 

 The feasibilily ofsecuring résistant varietics of colton by sélection aloiie is Unis 

 fuUy estabiished. Over 12 000 bushels of seed of the several résistant varietics 

 hâve been placed in Ihe hands of farmers Ihru llie Congressional Seed Distri- 

 bution, and Iheir cuUivation is now quile gênerai in localilies where wilt pre- 

 vails. 'l"he conlrol (il' will bas proved [lossilile in i<ei"'i"d farni prai'lise by Ihe 



.s. Ficlil or Ii-OM n.wiien. sliimiii;; 



lanci' 1(1 uill ,iiul roolkncl ;i- i oiii|i,ht'(1 willi tlie nnii-resisl.-iiil 

 vai'ieties on the riglit. 



l'Ig. S. — Cli.imp de Cowpea, variété "' Iron ''. nionlranl la résistance aux maladies comparée 

 avec (les variétés non résistantes (à droite . 



use of thèse resislanl sorts, combiiieil wilh rolaliun of crops hi iicep (hjwii liie 

 rootknol nematode. 



TJie numcrous liybrids llial wc liave ma(h' bclwccu the resislanl and iion- 

 resistant varietics of cotton liave given very contlicling results, se far as Ihe 

 inherilance of immunity as a Mendelian character is concerned. In shorl, 

 every culture gives a différent ratio between the number of liealthy and discased 

 plants. In gênerai the crosses behave as if résistance were dominant, but many 

 show variability due, doubtless, to Ihe gametic composition of the parents. 

 The subject is not an easy one. \Ve are dealing with an open ferlilized plant 

 of very complex gametic composition, and allho we used for crossing strains 

 that had becn line-bred for some years, vve cannot assert that they were 

 homozygous with respect lo will-resislance. The disease itself is sometimes 

 uncerlain in ils appearance. We cannot aKvays sélect land in which every sus- 

 ceptible plant will become infected, nor hâve we been able to secure accurate 

 counts of the plants that die. 



IV"' CUNFl n. IMF.IIN. PL (iKM^TKlUK. 17 



