POLLEN, OR FLOWER-DUST 97 



in themselves after they leave the ripe anthers, 

 althouo'h exceptions often occur. For example, 

 Fig. 61 shows an instance of compound pollen- 

 grains, though even these are really composed 

 each of four individual grains externally united. 

 Similar compound grains are found in some 

 orchids, while in others the whole of the pollen- 

 grains remain united into two club-shaped 

 masses, which become attached like two horns 

 to the head of the bee as it visits the flower, 

 and so are carried vvIkjIc to the sticky stigma ot 

 the next blossom it visits. 



To understand the structure of the pollen-grain 

 we must make a section (.)f it. This may seem an 

 extraordinary suggestion, considering that we are 

 dealing with a microscopic atom t(j commence 

 with. However, Fig. 62 shows several sections 

 of pollen - grains highly magnified. In these 

 examples it will be plainly seen that each grain 

 is surrounded by a cell-wall, the outer surface of 

 which bears the raised points, ridges, and other 

 markings found on the pollen-grain. Even this 

 simple-looking cell-wall is found to consist ot at 

 least two different layers of vegetable tissue when 

 seen still more highly magnified. 



Inside these protecti\'e layers is a dense mass ot 

 granular life-matter, or "protoplasm," which is 

 rich with starch grains and tiny drops of oil, and 



