OUTLINES OF BOTANY. 
XXIII 
ate length of the lower pedicels, so that the open cluster becomes broader 
than long and flat-topped or convei, as in the Hawthorn (p. 128). 
109. An Umbel further differs only in having the rachis (106) so short 
that the pedicels seem to spring all from the same point or nearly, and are 
mostly equal in length, as in the Primrose and Dodecatheon (p. 281). The 
bracts in this and the following case, being brought into a whorl (85) or 
cluster round the stem, form collectively the Involucre, as in the Prim¬ 
rose, Flowering Cornel (p. 168), &c. 
110. A Head (or Capitulum) is the same as an umbel with the pedicels 
all shortened, so as to bring the flowers into a solid rounded mass, or the 
same as a spike with a very short axis, as in the Clover (p. 106) and Teasel 
(p. 183). 
111. In these contracted or depressed forms, the older or lower flower- 
buds (107) will obviously occupy the margin or circumference, and they 
will expand in regular order from the circumference to the centre. Hence 
the indefinite inflorescence is sometimes said to be centripetal. 
112. Of the spike and head there are one or two particular forms ; such as 
the Spadix, which is merely a fleshy spike (as in the Calla and Indian 
Turnip, p. 446), or head (as in the Skunk-Cabbage, p. 447), usually envel¬ 
oped by a hooded bract (called the Spathe). 
113. The Ament, or Catkin, is the peculiar scaly spike of the Birch, 
Alder, Hazel, Willow, Poplar, and other amentaceous trees, &c. 
U4-. The compound flower of the older botanists, so familiar in the Sun¬ 
flower and all Composite (n. 184), is merely a head: the calyx-like scales 
(bracts) which subtend it form the involucre, and the broad or depressed 
rachis is commonly termed the receptacle. 
115. The bracts often borne on the peduncle or its branches are distin¬ 
guished by the name of Bractlets or Bracteoles. A stalk which 
Dears them is bracteolate. % 
116. From their axils branchlets in the form of flower-stalks may again 
arise, and so the inflorescence become compound. When, in such cases, 
the secondary division imitates the primary, there arises a compound spike , 
compound raceme (as in Smilacina racemosa, p. 491), or compound umbel 
(as in the Parsley and all that family, p. 153), &c. 
117. The secondary or partial umbels are called Umbellets. A sec¬ 
ondary involucre is termed an Involucel. 
118. If the lower branches of a raceme are branched irregularly, more or 
less, a Panicle is produced. A compact, pyramidal or oblong panicle is 
called a Thyrsus, as in the Lilac. 
119. In the definite, or second principal mode of inflorescence, where 
the flower-buds are all terminal (102), the main axis is first terminated by a 
blossom, which arrests its growth. This gives a solitary terminal flower, 
as in the Tulip, many Gentians, &c. Further development can take place 
only by the production of axillary branches; which can spring from the 
primary peduncle only when it is furnished with bracts from whose axils 
they may arise. They are most likely to spring from the axils of the up¬ 
per leaves. If the leaves and bracts are opposite (85), which is more com¬ 
monly the case in definite inflorescence, and a flower-stalk, or a branch 
terminated by a flower, springs one from each axil of the upper pair, a 3- 
flowered inflorescence is produced, in which the central (terminal) blos¬ 
som is earliest, and the two lateral (axillary) later, to appear and develop. 
The order of flowering is therefore from the apex downwards, or descend¬ 
ing (the reverse of the indefinite forms), or, if the three blossoms are on a 
level, from the centre outwards, or centrifugal. 
120. When the pair of leaves or bracts of the lateral branches or pedun¬ 
cles gives rise to new flower-stalks in the same way, a 7-flowered centrilu- 
