4 PLANT LIFE 



either (1) in the seed leaves, as in beans and peas, or (2) surround- 

 ing the parts of the plant, as in morning-glory seed. This store of 

 nourishment provides for the growth of the plant until it has devel- 

 oped enough to get its nourishment from the soil and air. 



Best Conditions for Germination. — A proper amount of moist- 

 ure is necessary to soften the seed coats and to provide for the cir- 

 culation of food which the seed contains. With many kinds of 

 seeds, such as melons, carrots, parsnips, salsify, celery, apple and 

 others, it is a very great aid to germination to soak the seeds in 

 water for a few hours before planting. Moisture is easily brought 

 to seeds through the soil when planted, if the soil is firmed. This 

 may be done with the fpot, hoe, or planting board. On large fields 

 farmers do this with rollers. 



aaQOKSSSQS! 



Fig. 1. — Cross section of leaf showing thick epidermis at top/ columnar cells, loose 

 parenchyma cells with air spaces, as at A ; thin epidermis below with breathing mouth or 

 stomate, S. 



In the cases of radish, lettuce, garden peas, onions, and others 

 which endure frost well, the seeds will germinate at rather low tem- 

 peratures. For this reason early garden crops may be planted in 

 early spring before the soil has become very warm. 



On the other hand, such seeds as corn, beans, tomato, and melon 

 will germinate much better if the soil is rather warm. It is partly 

 for this reason that such crops are started late in the spring. 



Air in the soil is necessary for the best germination of seeds. 

 They will not start well in soils that are so wet as to exclude the 

 air. A seed bed should be so well loosened by plowing or spading 

 as to allow the free access of air. See exercise 5. 



Parts of the Plant. — As the young plant grows it soon develops 

 roots, stem, and leaves. The roots serve to hold the plant in place 



