Seeds and germination 29 



preceding experiment. 17. What is the 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 air has been replaced by carbon dioxide. The air in the bottle may 

 be tested for carbon dioxide by removing some of it with a rubber 

 bulb qttached to a glass tube (or a fountain-pen filler) and bubbling 

 it through lime water. 18- Temperature. Usually there is a percep- 

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

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

 Goeds 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 re- 

 move 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 moulds and bacteria which might interfere with experiment.) 

 Peas or beans may be sprouted on damp blotting paper; the coty- 

 ledons of one may be removed, and this with a normal seed equally 

 advanced in germination 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. An- 

 other box of seedlings not so covered may be used as 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 

 <otyledons 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 w^hen mature on two- 

 year-old wood? How long do cones stay on a tree after the seeds 

 have fallen out? Wliat is the advantage of the seeds falling before 

 tne cones? 23. Home experiments. If desired^ nearly all of the fore- 



