STEMS OR TWIGS—WOODS. 61 
plants whose cotyledons in germinating do not appear above the 
surface of the ground); it can, however, also become extended, 
and then elevate the cotyledons far above the ground (in the 
Epigee,' for example, Linum, Vicia faba). 
The form of a transverse section of the stem structure is 
cylindrical or angular. In the latter case the position of the 
leaves stands in direct relation to the number of the angles 
(Labiate, with a quadrangular stem and cross-like arrangement 
of the leaves). On cylindrical stems the leaves are arranged in 
spirals. 
If the stems are developed in a leaf-like form, they are called 
phyllodia or phyllocladia’? (Ruscus, Australian species of Acacia 
Phyllocactus). 
In a pharmacognostical relation, the following organs of the 
stem come under consideration: 
Stems or Twigs (Stipites). By these names are desig- 
nated the weaker biennial and triennial, overground axes of 
dicotytedons, which are covered with an epidermis or cork, and 
contain chlorophyll. The only example properly considered 
here is presented by Stipes Dulcamare. 
Woods (Ligna). By wood is understood the mostly ‘‘lig- 
nified ” tissue (see below) of overground axes (or also of dicoty- 
ledonous roots), located inside of the cambium ring, which, with 
exception of the medullary rays, has attained considerable solidity 
through a material thickening of the cell walls. Only wood of 
many years’ growth of the Gymnosperms, as also that of the 
Angiosperms, serves for medicinal purposes, with or without 
the bark, occasionally also either entirely or partially freed from 
_ the outermost, younger layers, the so-called sapwood or albur- 
num (see Anatomy). 
Wood upon which the bark still remains, is frequently found in 
the two varieties of Lignum Quassie and in Lignum Sassafras, 
while Lignum Juniperi and Lignum Guaiaci are nearly always 
freed therefrom. 
The numerous dye-woods, as, ¢. 9-, Lignum Homgicey (log: 
!Exi upon or over, and yaia earth. wee. 
* SUAAor leaf, and xAaddos shoot orstem. 
