SEEDS AND GERMINATION 



29 



nature of the gas given off by germinating seeds ? Fill a tin box or 

 large-necked bottle with dry beans or peas, then add water; note 

 how much they swell. Secure two fruit-jars. Fill one of them a 

 third full of beans and keep them moist. Allow the other to remain 

 empty. In a day or two insert a lighted splinter or taper into 

 each. In the empty jar the taper burns : it contains oxygen. 

 In the seed jar the taper goes out : the air has been replaced 

 by carbon dioxid. The air in the bottle may be tested for 

 carbon dioxid by removing some of it with a rubber bulb attached 

 to a glass tube (or a fountain-pen filler) and bubbling it through 

 limfe water. 18. Temperature. Usually there is a perceptible 

 rise in temperature in a mass of germinating seeds. This rise may 

 be tested with a thermometer. 19. Interior of seeds. Soak 

 seeds for twenty-four hours and remove the coat. Distinguish 

 the embryo from the endosperm. Test with iodine. 20. Of 

 what utility is the food in seeds? Soak some grains of corn 

 overnight and remove the endosperm, being careful not to 

 injure the fleshy cotyledon. Plant the incomplete and also some 

 complete grains in moist sawdust and measure their growth at 

 intervals. (Boiling the sawdust will destroy molds and bacteria 

 which might interfere with experiment.) Peas or beans may be 

 sprouted on damp blotting paper ; the cotyledons of one may be 

 removed, and this with a normal seed equally advanced in germi- 

 nation may be placed on a perforated cork floating in water in 

 a jar so that the roots extend into the water. Their growth 

 may be observed for several weeks. 21. Effect of darkness on 

 seeds and seedlings. A box may be placed mouth downward 

 over a smaller box in which seedlings are growing. The empty 

 box should rest on half-inch blocks to allow air to reach the 

 seedlings. Note any effects on the seedlings of this cutting off 

 of the light. Another box of seedlings, not so covered may 

 be used for a check. Lay a plank on green grass and after a 

 week note the change that takes place beneath it. 22. Seedling 

 of pine. Plant pine seeds. Notice how they emerge. Do the 

 cotyledons stay in the ground ? How many cotyledons have 

 they ? When do the cotyledons get free from the seed-coat ? 

 What is the last part of the cotyledon to become free ? Where is 

 the growing point or plumule ? How many leaves appear at 

 once ? Does the new pine cone grow on old wood or on wood 

 formed the same spring with the cone? Can you always find 

 partly grown cones on pine trees in winter? Are pine cones 

 when mature on two-year-old wood? How long do cones stay 

 on a tree after the seeds have fallen out ? What is the advantage 

 of the seeds falling before the cones? 23. Home experiments. 

 If desired, nearly all of the foregoing experiments may be 



