56 
ORGANOGRAPHY. 
BOOK I, 
of annual duration from the surface of the earth are called 
herbs. 
Some botanists distinguish two sorts of stems, the characters 
of which are derived from their mode of growth. When a 
stem is never terminated by a flower-bud, nor has its growth 
stopped by any other organic cause, as in Veronica arvensis, 
and all perennial and arborescent plants, it is said to be in- 
determinate ; but when a stem has its growth uniformly 
stopped at a particular period of its existence by the production 
of a terminal bud, or by some such cause, it called determi- 
nate. The capitate and verticillate species of Mint owe their 
differences to causes of this nature ; the stem of the former 
being determinate, the latter indeterminate. 
The point whence two branches diverge is called the axil^ 
or, in old botanical language, the ala^ 
Leaf-huds (Gemma, Linn.; Bourgeon, Fr.), being the rudi- 
ments of young branches, are of great importance in regard 
to the general structure of a plant. They consist of scales 
16 17 
imbricated over each other, the outermost being the hardest 
and thickest, and surrounding a minute cellular axis, or grow- 
ing point, which is in direct communication with the woody 
and cellular tissue of the stem. In other words, they may be 
said to be growing points covered with rudimentary leaves for 
their protection, and to consist of a highly excitable mass of 
cellular substance originating in the pith, and having a special 
power of extension in length. Under ordinary circumstances, 
