3 



The ultimate branch, of the inflorescence of a grass is the 

 spikelet which is either borne on a stalk (or pedicel) or if there 

 is no stalk is said to be sessile. It consists of an axis, known 

 as the rachilla, which bears modified leaves or bracts arranged 

 alternately. The lowest two bracts have no flowers in their 

 axils and are known as glumes, the succeeding bracts have 

 flowers, arjd are known as valves. 



There are, however, the following occasional variations: 

 (1) one or both the glumes may be absent or minute, and (2) 

 one or more of the valves may have the flower imperfect or 

 absent altogether. In the latter case the valve resembles a 

 glume and is said to be empty or barren. 



Either the glumes or the valves may be prolonged down- 

 wards at the point of their insertion on the rachilla into a 

 ■ callus. 



Either the glumes or the valves or both may be prolonged 

 upwards into a short mucro or longer awn. 



Between each valve and the axis there is another bract 

 called the pale which is sometimes small or absent. The 

 flower is borne between the valve and the pale. 



The separation of the different species depends chiefly on 

 the characters of the glumes and valves, and the mode of 

 arrangement of the spikelets in the inflorescence, but some- 

 times the characters of the flowers or seed are of importance. 



The perfect (or hermaphrodite) flower consists of two 



minute scales called the lodicules, usually 3 stamens (rarely 



1, 2, 4, or 6), and a single ovary. Each stamen consists of an 



anther, borne on a slender filament. The ovary bears two 



"feathery styles (rarely 1 or 3). 



Male flowers have stamens only. Female flowers have 

 the ovary only. 



The fruit (or so-called seed) is called a caryopsis, and 

 has the seed coat adhering to the fruit wall. In a few cases 

 the seed is free inside the fruit wall, and the fruit is called a 

 utricle. The flowering axis is the culm. In perennial grasses 

 there are innovation shoots which grow into culms in the 

 •second year. The innovation shoots either pierce the sub- 

 tending leaf sheath, and grow up outside it (extravaginal), 

 or they grow up between it and the culm (intravaginal). This 

 feature is important in connection with plant succession and 

 in the study of the effects of grass burning, etc. 



