CHAPTER V.
CLASSIFICATION.
The family Gramineæ is usually divided into two series taking into consideration the presence or absence of a joint in the pedicel or rachis, the number of flowers in the spikelet and the position of the fertile flower. All the species in which there is a joint just below the spikelet, in the pedicel, in the rachis, or at the base of a cluster of spikelets come under one series Panicaceæ. The spikelets of the grasses coming under this series, when mature, fall away singly by themselves, or with their pedicels, or in groups with portions of the rachis. The spikelets are all similar and consist of usually four glumes. Each spikelet contains a single perfect flower and sometimes in addition a staminate flower just below the perfect flower. In this series the tendency for imperfection is always confined to the lower flowers, the terminal flower alone being perfect. For inclusion under this series the grass plant should have both the characters, articulation and position of the flower as mentioned above.
The second series Poaceæ includes those grasses in which the spikelets are one to many-flowered and continuous with their pedicels. But the rachilla of the spikelet may be jointed just above the empty glumes or between the flowering glumes. The complete flower is the lowest and the tendency for imperfection is in the upper flowers.
Of the two series the Panicaceæ appears to be more highly developed than the Poaceæ.
KEY TO TRIBES.
Series I.—Panicaceæ.
- A. Rachis of inflorescence not jointed.
- Spikelets 2-flowered; upper flower bisexual and lower male or neuter; the first glume the smallest I. Paniceæ.
- Spikelets 1-flowered;
- B. Rachis of inflorescence usually jointed.
- Spikelets usually binate (3-nate at the top), pairs of spikelets alike or dissimilar; empty glumes larger and the flowering glumes smaller, hyaline, the fourth glume awned or reduced to an awn IV. Andropogoneæ.
Series II.—Poaceæ.
- A. Rachilla produced or not beyond the flowering glume.
- Spikelets 1-flowered, with three glumes; first and second empty, third flowering and awned; rachilla jointed V. Agrostideæ.
- Spikelets 1- or more-flowered, biseriate and secund on an inarticulate spike or on the spiciform branches of a slender panicle; flowers all or the lower only bisexual VI. Chlorideæ.
- B. Rachilla produced beyond the uppermost flowering glume and articulate.
- Spikelets 2- or more-flowered, pedicelled, rarely sessile, in effuse, contracted or rarely spiciform panicles VII. Festucaceæ.
- Spikelets 1- or more-flowered, sessile, 1- to 2- or more-seriate on the rachis of a simple spike, or partially sunk in cavities of the same. Glumes awned or not, first and second glumes are opposite or subcollateral, persistent or separately deciduous; first glume minute or absent VIII. Hordeæ.