22 



SEEDS AND SEEDLINGS 



11. Germination of the Morn- 

 ing Glory. At the 

 left, the seedling as it 

 appears when breaking 

 • from the soil ; at the 

 right, the same seedling 

 a little later, the seed 

 coats thrown off, the 

 stem straightened, and 

 the cotyledons opened. 



variety of methods. When the cotyledons are designed 

 to act in the sunlight as green foliage for a time, they are, 



in general, brought out of the 

 ground by the lengthening of the 

 caulicle. As it grows, this usually 

 bends abruptly just below the 

 cotyledons ; and the top of the 

 loop thus formed is seen when 

 the cracking of the soil allows 

 one the first sight of the springing 

 seedling. The extraction of the 

 leafy parts is thus managed with 

 the least danger of injury from 

 the resistance of the soil (Fig. 11), 

 and at the same time the seed 

 coats are often slipped off. 



25. The main part of the origi- 

 nal seed may remain permanently 

 buried, while the nutrient con- 

 tents are gradually absorbed and carried away to the 

 actively growing regions of the root and the ascending 

 shoot. This is the case in the Horse-chestnut. The coty- 

 ledons are mere reservoirs of food. 

 Their stalks elongate (see Fig. 12), 

 freeing the caulicle and plumule 

 from the shell. The radicle develops 

 strongly, and the plumule rises, 

 looped, toward the surface. 



26. The end of the radicle for a 

 greater or less length, according to 

 the size of the plant, is always elon- 

 gating in growth, and slipping forward 

 between the particles of soil, which it 

 avoids or pushes aside* as the occasion 

 demands. A portion just behind this smooth thrusting 

 tip, having become fixed in position, throws out a velvety 

 coating of so-called root hairs. These penetrate sidewise 

 into the minutest interspaces of the soil, and adhere to 



12. Germination of the 

 Horse-chestnut. 



