62 
ORGANOGRAPHY. 
BOOK I. 
the air. While this ascending tendency is by many plants 
maintained during the whole period of their existence, by 
others it is departed from at an early age, and a horizontal 
course is taken instead; while also free communication with 
light and air is essential to most stems, others remain during 
all their lives buried under ground, and shun rather than seek 
the light. From these and other causes, the stems of plants 
assume a number of different states, to which botanists attach 
particular terms. It will be most convenient to divide the 
subject into the varieties of — 
1. The subterranean stem; and, 
2. The aerial stem. 
The SUBTERRANEAN Stem, often called souche by the French, 
was confounded by all the older botanists, as it still is by the 
vulgar, with the root, to which it bears an external resem- 
blance, but from which it is positively distinguished both 
by its ascending origin, and by its anatomical structure. 
{See Root.) 
23 24 
The following are the varieties which have been distin- 
guished : — 
The CormicSi fig. 23. (Lecus of Du Petit Thouars, Plateau 
of De Candolle), is the dilated base of the stem of Monocoty- 
ledonous plants, intervening between the roots and the first 
buds; and forming the reproductive portion of the stem of 
