Appendix E 425 



STUDY OF FLOWERS (prerequisite to crossing) 



Flower 

 Non-essential organs 



Calyx composed of sepals. 

 Corolla composed of petals. 



Essential organs 



Pistil - f carpels, 



a, style ; b, stigma ; c, ovary < placenta. 



I ovules. 

 Stamens composed of 



f loculus or cell. 

 a, filament ; b, anther < .. 



Degree of cross-relationship. 



1. Self- or close-fertilization. (Occurring in perfect or her- 

 maphrodite flowers.) 



2. Cross-fertilization. (Between individuals of same species 

 or variety.) 



3. Hybridization. (Between species and sometimes between 

 varieties which are very distinct.) 



Causes of sterility. 



1. Stamens and pistils maturing at different times. (Di- 

 chogamy.) 



2. Lack of affinity between pollen and stigma. 



3. Scanty or insufficient pollen. 



4. Lack of viability of pollen. 



Relative position between stigma and anthers. 



1. Stigma and anthers the same height. 



2. Stigma above anthers. 



3. Stigma below anthers. 



