THE SEED, GERMINATION AND THE PL ANT LET 25 



provide a damp atmosphere above them by covering with a 

 bell-jar or otherwise, for light does not hinder germination. 

 One of the interesting facts connected with germination 

 is, that the first shoot, called 



40. The hypocotyl grows downward on emerging from 

 the seed-case (27), no matter in what position the seed 

 is placed. It will curve in a semicircle if necessary, 

 to bring its rounded point in contact with the soil. 

 But the hypocotyl is not always able to enter the soil, 

 unless the seed is covered more or less, because the resist- 

 ance offered by the soil is often greater than the weight of 

 the seed. On this account, as well as to insure a supply of 

 moisture, it is best to cover most seeds at planting, or at 

 least to press them well into the soil (51). In nature, seeds 

 usually become more or less covered, and those not 

 covered generally fail to germinate. 



41. The seed-case in germination. After germination 

 commences, the seed-case is of no further use. It has 

 fulfilled its purpose, which is to protect the seed from the 

 time of its maturity until the conditions arrive for germina- 

 tion, and is henceforth a hindrance to germination in many 

 plants, as it must be torn asunder by the expanding plant- 

 let. If we watch the germination of squash or pumpkin 

 seeds through the different stages, we may discover that 

 nature has made a special provision to help the plantlet 

 in escaping from the seed-case in these plants. As the 

 hypocotyl curves downward, a projection or hook is formed 

 on the side toward the seed, which holds the seed-case 

 down while the seed-leaves are pulled out from it. The 

 action of this hook is shown in the accompanying figures. 

 Sometimes, as shown in C, the point of the seed-case 

 breaks, permitting the hook to slip off, and if the seed 

 happens to be planted edgewise or with the point down- 



