228 PRACTICAL LESSONS IN SCIENCE. 



Make a transverse and longitudinal section of an acorn, and 

 notice the pericarp or shell, the thin, brown membrane investing 

 the kernel, called the testa, and the whitish substance making up 

 the bulk of the seed which constitutes the cotyledons, with their 

 store of food for the young plant. Soak the seed of an acorn for 

 several hours in water and it can easily be separated into two 

 parts, but notice that they are united, study this bond of union, 

 and make out the radicle and plumule of the embryo. 



Make a transverse section of an oak stem and note the rings 

 of growth, the medullary rays, the numerous very large openings 

 which are pitted vessels, and the smaller ones, some pitted ves- 

 sels and some tracheids, and wood fibers. Note that the rings of 

 growth are not of uniform thickness, and an individual ring is 

 not uniform throughout. Find out the reason. Make a longi- 

 tudinal section through the heart and notice the numerous shiny 

 plates, the silver grain, or medullary rays. Sometimes the oak 

 has a strong taproot with few spreading ones. Occasionally the 

 taproot is replaced by spreading multiple roots. Find out a 

 reason for the difference. 



Oak timber is usually heavy, tough, durable and beautiful. 

 These qualities make it a valuable tree. It has a history; it is 

 famous in poetry and prose alike; it is especially interesting to 

 us as its history runs back through the early English and Anglo- 

 Saxon periods, and backward to our Aryan forefathers. The 

 tree has always been admired for its qualities, and it has often 

 been invested with superstition and romance. 



The oak grows best in the cooler regions ; it is generally de- 

 ciduous, but many evergreen varieties exist. It varies in size 

 from a tiny shrub to the sturdy forest tree sometimes six to 

 eight feet in diameter. It grows in a great variety of soils, and 

 varies greatly in quality and appearance. There are some 250 

 species of oak which are found mainly north of the equator; 

 about 100 species are found in the United States. The White 

 Oak and its varieties furnish the best timber. The Live Oak of 

 our southern states is especially valuable for shipbuilding. But 

 nothing in North America quite equals the Quercus rohvr. the 



