4 THE STORY OF PLANT LIFE 



hours and then placed between the blotting paper 

 and the glass. 



It is proposed briefly to outline the germination of 

 a pea, a mustard seed, and a grain of wheat. 



The first sign of germination in a pea (see Fig. 3) 

 is the splitting of the skin in the neighbourhood of 

 the radicle. The radicle itself soon emerges and 

 grows downwards. From one to two days later a 

 curved stem-like structure pushes out of the seed 

 above the stalks of the cotyledons. This is the 

 epicotyl ; in plants grown in soil it appears above the 

 ground as a little loop. As the epicotyl grow s longer 

 the plumule emerges from the seed and at length 

 appears above the soil. The epicotyl then straightens 

 itself, the plumule becomes erect and begins to 

 develop. The first leaf structures are small. They 

 become separated by the growth of the first internode. 

 As the second internode grows the first true leaf 

 gradually unfolds. The radicle meanwhile will have 

 grown in length, root-hairs will be distinguishable a 

 little way above the root-tip, and on the older part of 

 the radicle branches may have already appeared. As 

 the plant grows and other leaves unfold the root- 

 system will also develop, but the main axis of the 

 root will remain distinct even though numerous 

 branches are formed. 



In this type of growth the cotyledons are said to 

 be hypogeal, as they remain enclosed in the seed while 

 germination goes on. 



In the mustard also (see Fig. 3) the radicle is the 



