22 



SEEDS AND SEEDLINGS. 



as the opening 1 in the seed-coat or not?). The stalk of each 

 cotyledon grows in length, pushing the cotyledons apart and 

 allowing the curved shoot to grow out between them. What 

 is the advantage to the young plant in the fact that the 

 root emerges before the young shoot ? What advantage is 

 there in the hooked form of the young shoot ? 



Make Sketches (in this case twice the natural size will be large 

 encmgh) of (1) entire seed from the scar end ; (2) same from the front, 

 i.e. thicker edge, showing the pore and the bulge caused by the root; 

 (3) same in side view ; (4) side view showing the triangular flap being 



B 



Fig. 14. Stages in Germination of Broad Bean Seeds, planted in various positions. 



pushed off by the growing root ; (5) front view showing the same ; (6) 

 side and (7) front views of embryo after removing seed-coat ; (8) scar- 

 end portion of empty seed-coat, showing the pocket into which the root 

 fits ; (9) side and (10) front views of embryo with one seed-leaf broken 



1 The erroneous statement that the radicle grows out through the 

 micropyle in germination is often made in books. This opening in the 

 seed-coat doubtless helps the swelling radicle to split the coat, since it 

 forms a weak spot, but a glance at a Broad Bean seedling shows that 

 the coat splits along the edge of the radicle-pocket, the line of weak- 

 ness, and that the split does not reach as far as the micropyle* 



