UTILIZATION 



155 



vascular plants, and many others have made a tacit renuncia- 

 tion. To say that all the figures that have been drawn have 



Pt 



FIG. 71. Double fertilization. A, Helianthus annuus, showing the two coiled male 

 nuclei, one fusing with the egg-nucleus and the other with the endosperm nucleus ; 

 after NAWAscniN. 40 B, Iris, the two polar nuclei not yet fused; after GuioxARD. 32 

 (7, Silphium laciniatum : sp^ sp%, male nuclei : 0, oosphere ; 0, endosperm nucleus ; 

 sy, synergid ; pt, pollen- tube ; x, two conjectural bodies often seen in the pollen- 

 tube after the male nuclei have been discharged ; x 525 ; after LAND. 38 



been mere products of the imagination would be a radical state- 

 ment, and one doubtless very far from the truth. In our 

 opinion the observations, figures, and descriptions, like the 

 pollen-tube embryos of Schleiden and Schacht, furnish an exam- 

 ple of the extent to which even a careful and conscientious 

 scientist may be influenced by preconceived opinion. 



Our knowledge of the phenomenon called " double fertili- 

 zation " (Fig. 71) dates from 1898, when Nawaschin S3j 34 an- 



