SUNFLOWER STEM 55 



the surface hirsute. The arrangement of the leaves at 

 the lower part of the plant (and including the coty- 

 ledons, which wither at an early stage) is opposite, 

 or in whorls of three; higher up, this arrangement 

 merges gradually into the alternate. 



The stem is terminated by a bud, which may con- 

 sist only of closely aggregated foliage leaves, or it 

 may inclose the reproductive organs, which are 

 contained in numerous flowers, closely aggregated so 

 as to form a characteristic inflorescence the capi- 

 tulum. Similar buds, in earlier stages of development, 

 may be observed in the axils of the leaves (axillary 

 buds). 



Wash the roots and examine them. They are 

 fibrous, and branch profusely. The primary (tap) root, 

 and earlier developed lateral roots are thicker than 

 the later developed roots of a higher order, the 

 latter being successively thinner. This is due to 

 the fact that the roots undergo a process of secondary 

 thickening. 



* The Mature Stem. 



II. Cut the stem of a well-grown plant transversely 

 at its thickest part, and smooth the surface with a 

 razor. 



The most prominent object in the section will be the 

 massive, white, spongy pith which occupies the centre. 



Around this will be seen, arranged more or less 

 regularly in a circle, and near the periphery, a series 

 of more solid-looking masses of tissue ; these are the 

 vascular bundles. 



