n the Calla, Indian Turnip, (Fig. 206), Sweet
Flag, etc. It is commonly surrounded or embraced by a peculiar
enveloping leaf, called a SPATHE.

[Illustration: Fig. 206. Spadix and spathe of the Indian Turnip; the
latter cut through below.]

213. =A Catkin, or Ament=, is the name given to the scaly sort of spike
of the Birch (Fig. 207) and Alder, the Willow and Poplar, and one sort
of flower-clusters of the Oak, Hickory, and the like,--the so-called
_Amentaceous_ trees.

[Illustration: Fig. 207. Catkin, or Ament, of Birch.]

214. _Compound_ flower-clusters of these kinds are not uncommon. When
the stalks which in the simple umbel are the pedicels of single flowers
themselves branch into an umbel, a _Compound Umbel_ is formed. This is
the inflorescence of Caraway (Fig. 208), Parsnip, and almost all of the
great family of Umbelliferous (umbel-bearing) plants.

[Illustration: Fig. 208. Compound Umbel of Caraway.]

215. The secondary or partial umbels of a compound umbel are UMBELLETS.
When the umbellets are subtended by an involucre, this secondary
involucre is called an INVOLUCEL.

216. A _Compound raceme_ is a cluster of racemes racemosely arranged, as
in Smilacina racemosa. A _compound corymb_ is a corymb some branches of
which branch again in the same way, as in Mountain Ash. A _compound
spike_ is a spicately disposed cluster of spikes.

[Illustration: Fig. 209. Diagram of a simple panicle.]

217. =A Panicle=, such as that of Oats and many Grasses, is a compound
flower-cluster of a more or less open sort which branches with apparent
irregularity, neither into corymbs nor racemes. Fig. 209 represents the
simplest panicle. It is, as it were, a raceme of which some of the
pedicels have branched so as to bear a few flowers on pedicels of their
own, while others remain simple. A _compound panicle_ is one that
branches in this way again and again.

[Illustration: Fig. 210. Diagram of an opposite-leaved plant, with a
single terminal flower. 211. Same, with a cyme of three flowers; _a_,
the first flower, of the main axis; _b b_, those of branches. 212. Same,
with flowers also of the third order, _c c_.]

218. =Determinate Inflorescence= is that in which the flowers are from
terminal buds. The simplest case is that of a solitary terminal flower,
as in Fig. 210. This stops the growth of the stem; for its terminal bud,
becoming a blossom, can no more lengthen in the manner of a leaf-bud.
Any further growth must be fro