36 THE AMERICAN BOTANIST. 



and date during germination but in the ordinary high-school 

 course these may be disregarded since they are special cases 

 and have no place in the functions of the great majority of 

 seeds. 



That seeds need moisture to grow is a fact familiartoevery 

 high-school student; as to how much they need and how they 

 obtain it, the conception is not so clear. We may discover 

 how much water a given seed will absorb by weighing a quan- 

 tity of the seeds, placing them in water for a day, and after 

 wiping the moisture from the outside weighing again. Seeds 

 will usually take up more than their weight of water. To 

 decide where water enters the seed we may place some dry 

 seeds in colored water and note the path colored. The seed 

 of the white lupine, sold by most seedsmen is excellent for this 

 purpose though any large seed will do. In the absence of the 

 lupine, the common white or navy bean may be used but care 

 should be taken to see that the testa is intact. In many seeds 

 the testa swells up in ridges along the path of the water and 

 will show its course without the use of coloring matter. If 

 it is desired to discover whether the micropyle and hilum are 

 of any special advantage in absorbing water the behavior of 

 a set of seeds in which these parts have been covered up with 

 wax or rubber cement may be compared with that of a set 

 which have not been treated thus. Or one set of seeds may be 

 partly immersed in moist sand with their micropyles exposed, 

 while the other has the micropyles buried in it. It can be 

 shown easily that ordinary dry seeds contain water by putting 

 some seeds in a test tube and heating over a flame, first plug- 

 ging the mouth of the tube with a tuft of cotton. Moisture 

 will then condense on the cooler part of the tube. Notwith- 

 standing this, seeds once started to germinating will die if 

 dried and this may be proven by experiment. 



In many studies of seeds it is usual to prove that the stored 

 food is necessary to the young seedlings by cutting off one or 



