l8o THE TEACHING BOTANIST 



against the glass, and, growing against it in their descent, show 

 the positions and mode of branching of the roots most beauti- 

 fully. One of these boxes is supplied to each student, who 

 uses about half of the material, and has it again for the work of 

 the next week, the box in the meantime being returned to the 

 greenhouse, and the seedlings grown on as far as possible. 

 The boxes, if made in quantity at a box factory, cost complete 

 about 12 cents each, and of course can be used many years. 

 The value of supplying to each student his own set of living 

 and growing specimens in a box so arranged as to show the 

 under-ground as well as above-ground parts, is very great, and 

 amply worth the cost and trouble. If this system is not used, 

 the teacher should have some seeds grown in one such box 

 for all the students to see. The advantage of using the moss 

 instead of earth is obvious ; it is lighter and cleaner, and the 

 specimens can be removed from it without injury. 



Pedagogics. This outline can be completed in three two- 

 hour periods. It is to continue training in observation and 

 comparison, but especially is an introduction to the morpho- 

 logical and ecological principles controlling the unfolding of 

 the seed into the adult plant, and (most important of all) is an 

 introduction to the nature of irritability, which in plants answers 

 to sensation in animals. 



The students should not fail to notice that the root, the 

 root hairs, the turning green of parts exposed to light, the axil- 

 lary buds of the cotyledons in the brown bean, and the partial 

 disappearance of food substance are new features. They should 

 especially see that it is the elongation of the hypocotyl which 

 raises the cotyledons in Lima Bean and Morning-glory, while 

 it does not increase at all in length in the Horse Bean and 

 Corn. The root is, of course, a new structure developed from 

 the lower end of the hypocotyl, and its beginning is usually 



