INTRODUCTORY LESSONS. 



XI 



the side of this tube below the cotj-ledons, instead of 

 bursting through between them. 



Do not fail to see for yourself how squash 

 embr3'0s pvy open their tough coats. Soon after the 

 sprout has gained a foothold in the soil, a little knob 

 grows on the side of the radicle so as to split more 

 widely open the point of the seed coat, as s'lown in Fig. c. 

 Then tbe radicle stem between the knob and the cotyledons, 

 by growing, pries the seed still wider open, as seen at 6 below. 

 Finally, by continued growth, the cotyledons are pulled out 

 of the seed coat and upward to the surface of the ground, 

 where they expand, and become pretty good leaves. Seeds 

 jDlanted edgewise, which of course could rarely happen in nature, can not 

 thus free themselves of their seed coats, and it has been proved by a 

 French botanist (M. Flahault) that seeds which come up with their coats 

 on do not thrive. The seed at b in the figure was first planted the other 

 side up. It was turned over when the knob on the right had begun to open 

 the seed. The radicle, which then pointed directly upward, gradually 

 straightened, bent downward, and finally the second knob grew, by the 

 help of which the seed leaves were in a fair way to get out when the draw- 

 ing was made. Some native California plants get 

 out of their coats in a similar manner. 



Germination of Albuminous Seeds. 

 You have observed that when seeds without al- 

 bumen send their cotyledons above ground, the 

 seed coats are usually lieft behind, but the albu- 

 minous seeds named in paragraph 5 retain their 

 seed coats often for several days after they come 

 up. Examine the coats after they are thrown off, 

 and you will find none of the albumen which 

 formed the larger part of their contents before 

 germination. The enlarged cotyledons tell what 

 has become of it, and it is now plain why the 

 coats were retained. 



