DEFINITE OR DETERMINATE INFLORESCENCES. 209 
partial umbels or wmbellules. When the base of the general 
umbel is surrounded by a whorl of bracts (fig. 398, a) they 
constitute a general involucre ; and if other bracts, b, 6, are ar- 
ranged in a similar manner around the partial umbels, each of 
these whorls of bracts forms an involucel or partial involucre. 
These varieties of arrangement have been already alluded to 
when speaking of bracts (page 195). 
Fie. 430. 
Fig. 430. Compound umbel of Fennel. a. General umbel. 86, }, b. Partial 
umbels or umbellules.—/Fg. 431. Portion of the floral axis of a species of 
Gentian (Gentiana acaulis), terminated by a solitary flower, below which 
are two bracts. 
2. DEFINITE, DETERMINATE, OR TERMINAL INFLORESCENCE. 
In all kinds of definite inflorescence the primary axis, as we 
have seen, page 201, is arrested in its growth at an early age by 
the development of a terminal flower-bud, and if the axis bears 
no other flower this is called a solitary terminal flower, and is 
the simplest form of this variety of inflorescence. Examples of 
this may be seen in the Stemless Gentian (jig. 431), and in the 
Wood Anemone (Anemone nemorosa). When other flowers are 
produced on such an axis, they must necessarily arise from axil- 
lary flower-buds placed below the terminal flower-bud ; and if 
these form secondary axes (jig. 432, a’’), each axis will in like 
manner be arrested in its growth by a terminal flower-bud f” ; 
and if other axes @’”’ are developed from the secondary ones, 
these also must be axillary, and will be arrested in a similar 
manner by flowers f’”’”, and these axes may also form other axes 
of a like character, and so on. Hence this mode of inflorescence 
is definite, determinate, or terminal, in contradistinction to the 
former or indefinite mode of inflorescence already described, where 
the primary axis elongates indefinitely unless stopped by some 
extraneous cause. Definite inflorescences are most common and 
regular in plants with opposite or whorled leaves, but they also 
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