.{SO NIELS NIKLSKN 



twn niicli'i Itirmcd l'\ Ih«' lulcrolypicMl division now dividc siiniil- 

 l:iiu'(»iisly in Iwos. ;nul \hv Imn- nncici Iniinrd l>y liir li(»nn)('<)ty|)i('ai 

 di\isinn :\rv arranj^cd likc llic corncrs ol a tctrahcdon. Now (Iic 

 pollen niothrr nll di\idfs siiiudtanroiisly inio 4 ^lobular-lclrahcdal 

 danf^lilcr-jflls. 



THE CHROMOSOME NUMBER. 



As Ulf chroniosonit's wvvr rallicr bii,' and not vt-iy nnmerons. il 

 was n<»l diiricull lo ascrrlain llicir nnnihcr. Only willi rc^Jird to 

 llyprrictini pcrjordtiiiu somo dillicully was mel willi: in most cases 



16 chroniosonu's wcn- dislinctly scrn. bul in a Icw casi's Ihcrc were 



17 or IS chroinosomcs: llic ^»rcati'r ninnber ol)served in these cases is 

 prol»ai)ly an irrcj^'uiaiily. and HypcrUum pcrforalum has no doul)! 16 

 chroinosonu's normally. 



in llic lollowin^,' lal'lf tlic hai)loi(l nunibcr ol" clironioscjmes is 



f^iven. 



X 



Sccl. lioscifiui: II. Ascyroii L. 9 



Scct. Aiidrosdctxiim: 11. .Xndrosaemum \j. 20 



//. hirciniim L. 20 



//. iiKxloniin WiLLD. 20 



Scct. l^iiln/piTiciiiu: II. coris L. 9 



//. })()h]j)hiiUum Hoiss. cl Ual. 9 



//. Iiir.siiliim L. 9 



//. ludciildliim (Avrz. 8 



//. (uiilmn MoENCH. 8 



H. inontanum L. 8 



H. tomcntosnin L. 8 



//. pcrfordliini L. 16 



//. oriydiiifolimn WiLLl). 9 



//. oricnldlc L. 8 



//. rnnicUciiiu Hoiss. 7 



Sccl. Mijridmhd: II. jirolificimi L. 9 



Tlic rulc li:is l)c«'n laid down (WiNGK 19171 thai Ihc chromosomc 

 ntmihcrs wilhin a ^cnns or liimily stand in dirccl proportion lo cacii 

 othcr. The chromosomc ninnhcrs shonid l»c terms in an arilhmctic 

 series, and. consecpicnily. Ihcy may he tmnid hy mnlli|)lyinj^ a certain 

 radix Tor the j^'ronj) l.v diHeren| w hole liL'urcs. Tliis rnie is hased on 



