210 PRACTICAL BOTANY. 



Obtain the ripe or nearly ripe seeds from a two-years- 

 old cone. Notice the wings and the markings on the sur- 

 face of the seed. Of what use are the wings? Make a 

 section of a seed through the micropyle, and compare with 

 the observations made on the first and second year cones. 

 The integument has thickened greatly, and now consists 

 of two coats ; the nucellus has almost disappeared ; the 

 endosperm has increased in amount and firmness because 

 of the accumulated food supply for the new plant. 

 Macerate the endosperm in caustic potash and dissect it 

 with needles. Make out the embryo, and in it a number 

 of cotyledons and a radicle. 



6. Make thin longitudinal sections of an apical bud 

 that is, the winter bud from which the next year's new 

 shoot will develop which has been preserved in alcohol. 

 Mount in Schultze's solution all of the sections that are 

 cut through or nearly through the apex. Examine under 

 both low and high powers. Notice the thin- walled cells, 

 abundantly supplied with protoplasm, at the apex. In the 

 acrogenously growing plants of the lower subdivisions up 

 to the Lycopods, the growth in length originates in the 

 division of an apical cell. In the Phanerogams the thin- 

 walled cells near the apex of the stem are capable of divi- 

 sion. From their division arises the growth of the plant 

 in length. The apex of the stem is, therefore, called the 

 growing apex or the punctum vegetationis. The newly 

 formed tissue at and near the apex is the primary meristem. 

 Trace the differentiation of these cells as far back as your 

 section permits. Do you find tracheides and spiral ves- 

 sels? 



7. Study the foliage leaves. Measure a number of 

 leaves on each of two or three species of Pine. State 

 the average length for each species examined. What is 

 the shape of the end ? Notice rows of dots, the stomata, 

 running lengthwise the leaves. With a sharp razor cut 



