128 STRUCTURAL BOTANY 



that the whole tube is filled with protoplasm. The 

 protoplasm with the nuclei is at all stages of growth 

 to be found in the growing end of the tube. All the 

 older part of the tube is almost empty. 



It is quite easy to cultivate the pollen-grains and 

 make them germinate, if we provide them with an 

 artificial stigmatic fluid. All that is necessary is to 

 put some of the grains into a drop of sugar-solution 

 on a glass slide, so that we can observe them under 



FIG. 45. Pollen-grains of Wallflower germinating in 6 per 

 cent, sugar solution. Observe the three nuclei, two of 

 which are already in the pollen-tube. Magnified about 

 200. (R. S.) 



the microscope. For the Wallflower pollen a 6 per cent, 

 solution of common sugar (cane-sugar) is about right. 

 In this the grains will put out tubes which reach a 

 considerable length, and the passage of the nuclei 

 down the tubes can be observed. The pollen-tubes 

 figured (Fig. 45) were obtained in this way. 



The details of fertilisation have not been followed 

 in the Wallflower, which is not very favourable for 

 the investigation, as the structures in question are 

 email. What follows is a general description based 



