^ '•/ 



POLLEN GRAINS OF SEMI-STERILE PLANT. 



This remarkable photo-micrograph of pollen grains of a first generation Lyon x Velvet hybrid 

 shows strikingly the nature of the sterility, half of the sacs being empty. It was made by 

 staining the pollen yellow and then photographing it with blue glass on the condenser. 

 The si/.e of the grains can be accuratel}^ measured by the scale at the side of the photo- 

 graph, which is graduated in tenths and hundredths of millimeters. ''Figure 5a.) 



67 



