FIRST STEPS IN MICROSCOPIC MOTION PHOTOGRAPHY 99 



the external; the pollen grain tries to expand, the 

 outer skin not being elastic, bursts, and the inner 

 skin pushes out through the opening and continues 

 to grow in a tube-like shape, following the line of 

 least resistance or growing toward the stigma. If it 

 is near enough to attract it, the grain plus the grow- 

 ing tube is actually increased in volume on account 

 of the water taken in. It really begins active life in 

 the grain when the protoplasm, before inactive, or 

 resting, starts moving very rapidly, flowing out of 

 the grain into the tube, pushing its growing point 

 ahead. It seems to follow a definite channel, down 

 one side to the point and back on the other, enter- 

 ing the grain again in a never ceasing river of circu- 

 lating life. Just how the grain by absorbing the 

 sweetened water starts active from passive life is un- 

 known, presumably just as a grain of wheat or a 

 kernel of corn, given moisture and heat, achieves life 

 and begins its growth. 



The protoplasm seemingly in tiny globules having 

 a more or less granular appearance, does not move at 

 a uniform speed. It flows rapidly, almost stops, 

 seems at times to turn and retrace its flow, then as if 

 an obstruction were removed rushes forward again 

 like a freshet released by the thawing of an early 

 spring blockade. This circulatory movement goes on 

 in the sweetpea pollen for four or five hours, less and 



