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> oe * Structural et dt Physiological B Dota 
are “Gece stemless’ or acaulescent, with radical eaves 
only ; but this results from the stem remaining very short 
—and undeveloped in proportion to the root and leaves, and — 
a ae ‘therefore overlooked. Examples occur in /lantago, 
the turnip, [primrose], &c. 
Those stems which spring, on germination, directly from. 
_ the axisof the embryo|z.e¢. from its upper extremity or plumule] 
are called primary stems, and their ramifications secondary 
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ee vor lateral stems, or branches. ‘The position of the ‘branches 
on the primary axis determines what is called the habit of | 
the plant. They are said to be verticil/ate or whorled when 
several spring from the primary stem at the same he’ght, as in 
Equisetum ; opposite |as in the elder] when two opposite 
branches are always found at the same height ; decussate 
-when each opposite pair is at mght angles to those imme- 
diately above and below it, as in the lavender ; dichotomous’ 
when the stem repeatedly divides into two branches of equal 
thickness, as in the mistletoe ; scattered when the arrange- 
ment of the branches is apparently irregular.! It sometimes 
happens, especially in the inflorescence of rushes, that a 
lateral branch completely takes the place of a primary axis 
the development of which has been suppressed, and con- 
tinues its growth in nearly the same direction; and such a 
branch, which therefore consists of several successive se- 
-condary axes, 1s a sympodium. ‘The part of a stem which 
intervenes between two leaves is an znternode, [and the 
part from which a leaf springs is a ode]. The length of 
life of the stem and roots may be onlyasingle year, anual ; 
two years, bzennzal; or a number of years, perennial. 
The most completely developed form of the aérial 
| » (above- -ground) stem, the woody stem or zruk, is the cha- 
acteristic of ¢vees and shrubs. If the lower and smaller 
e part of the stem is woody, while the upper and larger part 
cet ‘This will be further explained when ppeaiiis of the arrangement of 
i ‘leaves tp.’ 37). 
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