398 l\ CdM'r.IlKNCK l\TKIlN\ll(iNM.r: m: CÎAKTK.il i:. 



ol' lliis rlas>- coMsidcnililc i;r;iiliiii; is ollrii l(i lie rimiid l'Vcii MiiKiiii^' llir llowcrs 

 ol' oiie iiidividiiiil. 



In thc cnse of classes tij and .") douldr^ l'au ]«■ dMainrd l'i-diii srcd: cillier 

 IVom Ihc seed of douhlcs whicli havc Kccii sell- or iidcr lurd (das- 7,} or |iid- 

 liiialed witli sinf>;les (flass2b); oi- IVoiii llic scod ol' siiit;lcs wliiili lia\(> Kccii 

 pollinaled willi dovdjles iclass 2 a). 



Din'ei'ing- in hohaviour from oarli ol' llics(> ly|irs howcvcr and slandiiiL;- (jiiilc 

 alone is Ihc geiiiis Malthinla. For licre, l/ioui/li Ike (IduIiIcs arc uf Ihr r./ireine 

 type described ahnve and form neither pollen nor ovvlcfi, they are nevertlieless 

 ohtained from Rccd, and moreovcr. from Ihc serd of sinf/les ferliliacd bij aini/lrx. 



In mosl. t;-ai'd('n l'omis ol" slocks (MaU/iiola) \\r niay disliniiiiisli Iwo kiiids 

 of singles. 



i) Ihe doiibl('-l/iroa<inij uv crersporliiu/ (=d-singlr) and, 



ii) the non double-tlnnivinij (= no-d-single). 

 which, Ihoiigh indislingiiisliable in appearaticc. diiïei' in hehaviour. Any indi- 

 vidual of eillier class prodiices successive générations of descendants siniilar in 

 behaviour to itself. 



The non-doulde-lliri)\ving single breeds Irue to singleness. '{"lie eversp(jr- 

 ting type gives a niixUiic of singles and douilles, Ihc doubles being sliglitly in 

 excess. 



We may illustrale Ihe dilVerence in liehaviour ol' lliese two slrains gia]ihi- 

 cally Ihus : 



Mi]|i-(l(>ulili'-liini\viiig single i;\fi-s|i(iriiii sinslo 



I 1 



siiÉt.'k'S siiiglus doublas (sier'lle; 



douilles :stci"ili' 



(Inulile 

 nilelinitelv 



Thus in eversporling singles we are dealing wilh a case in wliii li a cerlain 

 characler — doubleness — appears in a ddinile pi'o|ioilion ofllie oll'spring in 

 every génération, but in which no individuel exhibiling lliis characler is able to 

 transmit il, since such individuals can bave no descendants. In Ibe earliesl 

 record of Ibe double Stock known to us, wbicli dates back lo the niiddle of tlu; 

 IC)"' century, the llower is depicted like liic double of the présent day, as liaving 

 neither androecium nor gynoecium. iNow Huit experiment bas i-evealed the 

 peculiar relations of the faclors conccrned, and Iheir distribution among tiie 

 germ cells, \ve ai'e able lo explain this curions anomaly in the heredity of Stocks. 



W'iieii the two kinds of single are bred logelbcr, the resulting F, génération 

 is ail single. 



If the maling is in Ihe form : 



no-d-siiipk' 9Xd-siiif;le o' 



ail the Fj crossbreds give a mixture of singles ami doulilrs in V, -^/iniccall l/n: 

 pollen in d-singlet; miist carry '/om///c)u'.s.-;. 

 In the case of Ihe rcci|irocal maling : 



d-biiit;l(' î X iiii-d-siu^'lo ,-f 



