SUNFLOWER STEM 35 



ductive organs, which are contained in numerous flowers, 

 closely aggregated so as to form a characteristic inflorescence 

 the capitulum, or head. 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. 



III. In order to obtain a clear idea of the course of these 

 bundles along the stem, and of their connection with those of 

 the leaves, cut off a piece of the stem, so as to include the 

 insertion of a leaf or node, and about two or three inches of 

 stem above and below that point. Bisect this longitudinally in 

 a plane perpendicular to the median plane of the leaf, i.e. so 

 that one of the pieces will bear the whole base of the leaf. 

 Clear away the pith with some blunt instrument, taking care 

 not to injure the vascular bundles. This process will be made 

 easier if the stem be previously boiled in water for about ten 

 minutes. 



Now dissect out carefully the course of the several vascular 

 bundles, clearing away as much of the internal parenchyma as 

 possible. Treat the whole preparation with acid solution of 

 aniline sulphate for about five or 'ten minutes. The vascular 

 bundles will be stained yellow, and their course may then be 

 more readily followed. 



D 2 



