FLOWERS AND THEIR WORK. 215 



245. Fertilisation. In what way does the pollen-grain 



Fig. 69. Broad Bean : A and B, Cross-sections of Young Anthers ; 0, a Ripe 

 Pollen-grain ; D, Pollen-tube. 



induce the " young seed " (ovule) to develop into a mature 

 seed? What happens when a pollen-grain is placed on the 



B. 



J X 



VASCULAR BUNDLE POLLEN-TUBE 



IN STALK OF OVULE 

 Pig. 70. Development and Structure of Ovule (" young seed "), Longitudinal Sections- 



stigma? We cannot give a full answer to these questions 

 unless we study the minute structure of the parts concerned. 1 



1 Preparations of specimens showing fertilisation and embryo- 

 formation are included in the Plant Biology Set of Microscopic Slides. 



