RUNNERS AND STOLONS. 57 
also called root-fibres. Examples of primary roots are afforded 
by Radix Pyrethri, Rad. Scammonie, and Rad. Tarazaci ; 
excellent root-branches are possessed by Rad. Ratanhie, and 
root-fibres by Rad. Angelice. 
Secondary roots are such as originate laterally from the pri- 
mary root or from parts of the stem, and which, upon the 
whole, since the main root is often suppressed, occur much more 
frequently than the primary root; in those cases, therefore, 
where the distinction between primary and secondary roots is 
not sharply characterized, as with Rad. Angelice and Rad. 
Levistici, they may be designated simply as roots. 
Occasionally, only the secondary roots are collected, but for 
the most part the primary and secondary root together are offi- 
cinal. 
Above the tip of the root, mostly confined to small tracts, and 
advancing with the growth in length, are found the root-hairs, 
which individually (see Anatomy) become firmly attached in 
their growth to the particles of earth, and convey the dissolved 
nutritive substances of the soil to the root. 
The function of the root is to fix the plant in the soil (hence 
the central vascular bundle cylinder; see Anatomy) and to ab- 
sorb the inorganic nutritive substances and water from the soil. 
- The roots, as well as many rhizomes, are provided with a 
bark which, in some cases, is removed by paring before the 
drug is made use of (Althea, Glycyrrhiza, Iris), and in others, 
where it is rich in active constituents, it is allowed to remain 
(Calamus). Barks separated from the root are also officinal, 
thus, e. g., Granatum (Pomegranate), the bark of the root of 
Punica Granatum Lin. The root-bark of Krameria (Rhatany) 
was also formerly in use. 
Beside the true roots, there is still a series of underground 
formations, which belong, however, morphologically to the 
organs of the stem, even though they also fulfil physiologically 
the function of roots. These are the runners or stolons, rhi- 
zomes and tubers. 
The Runners (flagella) and Stolons (Stolones) which 
emanate from the root or from the base of the stem lie on the 
