HETEROSTYLY 47 
Among dimorphous flowers four modes of fertilization are possible, two of them 
legitimate, and two illegitimate. Darwin has represented the possible legitimate and 
illegitimate unions by the accompanying diagram (Fig. 5). 
Eighteen modes of fertilization are possible among trimorphous flowers, and of 
these six are legitimate. If we indicate the longest organs (é and 9) by J, the 
medium ones by m, and the shortest by s, and use a, 6, and ¢ to represent the 
long-styled, medium-styled, and short-styled forms respectively, the six legitimate 
crossings possible are as follows :— 
Z& (6) withZ 9. m & (a) with m 9. s 8 (a) with s 9. 
Vs a) Nee a MGC Vee Mae Se, RECO ig. OY OR: 
The twelve illegitimate modes of crossing are :— 
Z& (6) with'm 9. m & (a) with 7 9. s 6 (a) with 7 9. 
LBS) oR SO). MB BABY. 308 Bie SrONKA Is meng! 
Bento ys we) wees, et (3) Me aa oe) Od he ae aa oe 
FEB te). £79. MENG) 5 8 8 S11 (6) ts, ) emmy os 
The six legitimate modes of crossing have been schematically represented by 
Darwin in the following manner :— 
Fic. 6. Déagram showing the possible legitimate untons in a trimorphic plant (Lythrum 
Salicaria) (after Darwin). The arrows and dotted lines indicate the anthers from which the pollen 
must be brought to the stigma of one of the three forms, so as to give a legitimate union with complete 
fertility (Loew). (1) Long-styled form. (2) Medium-styled form. (3) Short-styled form. 
The results of numerous experiments carried out with the greatest care by 
Darwin and Hildebrand are as follows (according to Loew, ‘Einfithrung in die 
Bliitenbiologie,’ pp. 218-20) :— 
