CHAPTER IV. 



FURTHER GROWTH AND DURATION OF PLANTS. 



By the time the plant has germinated, that is, has unfolded the 

 parts formed in the embryo, and has used up the stored food, 

 the root, by means of the root-hairs, has become closely at- 

 tached to the soil. New roots are sent out with their root- 

 hairs, and the plant is able to get its own food material, partly 

 from the soil through the roots and partly from the air by means 

 of the leaves. While the embryo was unfolding, the plant was 

 not increasing in dry weight, but by the time the first new 

 leaves are forming the plant is beginning to add to its weight ; 

 growth has really begun. 



In none of the seeds studied were the cotyledons and plum- 

 ule similar in appearance. In the bean, after the two plumule 

 leaves, but one leaf unfolds at a time. There appear to be 

 three, but they are all borne on one leaf-stalk. Notice the little 

 cushion at the base of each part. 



One pupil kept her bean carefully watered. After a while 

 it bore branches. Each branch appeared in the axil of a leaf. 

 (The axil is the upper angle made by a leaf where it joins the 

 stem.) One day a white blossom was reported ; others fol- 

 lowed. They were short-lived, the pretty white part fell, and 

 she feared the plant would die. But in the centre of each 

 flower a pod came. Seeds appeared in the pods, and in each 

 seed a new bean life was formed. When the pods ripened, 

 they split open, and the seeds fell out. Then care and watch- 

 ing no longer availed. The plant's lifework was done. It had 

 borne fruit ; then it turned yellow, withered away, and died. 

 This all happened in less than a year. A plant which com- 

 pletes its life history within a year is called an Annual* Some 



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