258 GRASSES OF OHIO 



TERMINOLOGY OF THE GRASS INFLORESCENCE 



The inflorescence of a grass is made up of compact flower-bearing 

 branchlets known as spikelets. In general, the spikelet of a grass is of 

 the same importance in identification as the flower in most other groups. 

 The spikelet usually has two bracts at the base which are called the empty 

 glumes. These may be distinguished as the outer and inner empty 

 gl nines, or the lower and tipper empty glumes. Each flower is also nor- 

 mally inclosed in two bracts, called the flowering glumes. The outer of 

 these glumes is called the lemma, the inner the palet. All of these bracts 

 can thus be called glumes collectively. Through reduction of the spikelet 

 and degeneration of the flower, part of the glumes may be absent or 

 vestigial, or extra glumes may be present. Usually there are 2 (some- 

 times 3) minute bracts or scales at the base of the flower, within the 

 flowering glumes. These are called lodicules and are supposed to repre- 

 sent a vestigial perianth. The axis of the spikelet is called a rachilla and 

 if the inflorescence is a spike, its main axis is called a rachis. 



EXPLANATION OF PLATE XI 



Fig. 1. Diagram of spikelet of Bromus sp. 



Fig. 2. Diagram of spikelet of Panicum virgatum. The staminate flower has a 

 vestigial gynecium. 



Fig. 3. Diagram of spikelet of Chaetochloa viridis. The vestigial flower con- 

 sists only of a lemma. There are bristles at the base of the spikelet. 



Fig. 4. Diagram of staminate spikelet of Coix lacryma-jobi. Each of the two 

 flowers has a vestigial gynecium. 



Fig. 5. Diagram of carpellate spikelet of Coix lacryma-jobi, enclosed in a modi- 

 fied bony leaf sheath. The spikelet contains a vestigial lemma and a 

 carpellate flower with three vestigial stamens ; also two vestigial struc- 

 tures marked as oval black spots. 



Fig. 6. Spikelet of Bromus racemosus showing the two empty glumes and nine 

 flowers. 



Fig. 7. Lower or outer empty glume of Panicum virgatum. 



Fig. 8. Inner or upper empty glume of Panicum virgatum. 



Fig. 9. Lemma of Eragrostis major. 



Fig. 10. Palet of Eragrostis major. 



Fig. 11. The two lodicules (vestigial perianth segments) at the base of the grain 

 of Triticum aestivum. 



