354 



Plant Physiology 



Normal pollination takes place through the agency of 

 wind and insects, for the most part ; and it may be inter- 

 fered with by rain or other climatic conditions not resulting 

 in the death of the flower. Such conditions may close the 

 flowers, preventing the transfer of pollen ; or beating rains 



FIG. 98. Pistillate blossom of squash, showing large stigmatic surfaces. 



may wash the pollen from the stigma. In consequence, 

 orchards may fail to be productive through the effect of 

 climatic conditions upon pollination. 



206. Fertilization. Fertilization is the union and fu- 

 sion of two single gametic cells, or nuclei, which have 

 previously been differentiated by a special course of de- 

 velopment. In flowering plants the one gamete is derived 



