42 



Elementary Work in Botany. 



r 



Fig. 28. a. End of a board cut nearly parallel 

 with layers of growth, b. End of a board cut 

 nearly parallel with the medullary rays. A. 

 End of one-quarter of a log showing the char- 

 acter of the boards sawn from it. The straight 

 lines show the saw cuts and the curved lines 

 represent direction of annual growths. Boards 

 like a would be cut on the left, and boards like b 

 on the right. [See note in Appendix.] 



determine where the center 

 of the log must have been 

 from which it was sawn.* 



EXERCISE 25. 



[Read and discuss in the class.] 



Forms and Habits of 

 Sterns. Plants which die, 

 at least to the ground, after 

 they have matured fruit are 

 usually called herbs, and 

 their stems are said to be 

 herbaceous.^ Many such 

 plants live but one season 

 (usually five or six months) 

 and are called annuals. 



* Pupils may, by trial at home, determine for different kinds of wood 

 whether they split more readily along the lines of growth, along lines 

 radiating from the center, or along lines making an angle of forty-five degrees 

 with these. A piece of flooring, showing annual growths at the end, as seen in 

 the figure at a, and another, with the growths as shown at, might, with the well- 

 worn floor of the schoolroom, enable the pupils, and the teachers as well, to learn 

 a practical lesson on ' ' How to select boards for the floor of an uncarpeted room." 

 Find which boards have worn best in the schoolroom; those with the "grain" 

 like a or those like b. It is plainly shown in the figure that only part of a log 

 sawn in the usual way can be made into good flooring. 



Something about driving nails may be learned too. Evidently a nail 

 driven perpendicularly through boards, like a or b, would be more likely to split 

 them than if driven obliquely; but in a board with either the radial or the growth 

 lines not parallel with the sides, a nail should be driven perpendicularly. 



fHalf woody plants, like blackberries, often produce a stem one season 

 which after fruiting the next season dies. Such plants are not called her 1 s. 



