342 THE BIOLOar OF THE PLANT 



the length of these canals. Compare the diame- 

 ter of the canals with that of a starch grain. Are 

 the canals large enough to admit of a starch 

 grain passing through them from one cell into 

 the next? Can, then, the starch grains be car- 

 ried into and out of the cells by the flow of sap 

 through the tissues of the cotyledon ? 



Compare the results of all your experiments 

 on the dry seeds. Do you find starch present ? 

 Grape-sugar? Aleurone? In what form does 

 each of these exist in the seed ? 



PHYSIOLOGY 



a. Imhibition and turgescence. 



1. With a pair of dividers measure the length, 



width, and thickness of several dry beans, then 

 put them into a dish of water, and examine at 

 intervals of three to five minutes. Explain the 

 changes which take place. Let the beans re- 

 main in the water overnight. "What change ? 

 Explain. Compare the measurements of the 

 soaked with those of the dry beans. Is the 

 average increase in the size of the beans due 

 to the imbibition of water? Let the beans 

 dry in the air. Do they regain their original 

 size? 



2. Pack a thin glass bottle full of dry beans, pour 



in enough water to cover them, fasten the stop- 

 per tightly with a cord or wire, set the bottle 

 aside for a few hours, then examine. Explain 

 the result. Do seeds imbibe water in spite of 

 great external pressure ? Compare the behavior 

 of the seeds in this experiment with that of a 



