U 



SOUTH INDIAN GRASSES 



and the surface hollowed out, the spikelets fitting in the cavities 

 as in Rottboellia and Manisuris. 



In panicles, especially when they are diffuse, the primary 

 branches may be disposed irregularly or in verticils on the main 

 axis. For example in the panicle of Eragrostis Willdenoviana, 

 the branches are irregularly disposed, whereas in Sporobolus 

 coromandelianus the branches are verticillate. In both these 

 grasses fleshy cushions are developed in the axils of the branches. 

 These swellings help to spread out the branches especially at the 

 time of anthesis. The branches at the top spread out earlier than 

 those below. 



Sometimes at the base of the rachises, main or secondary, 

 glandular streaks are seen as in the rachises of Sporobolus coro- 

 mandelianus. These glands secrete a viscid juice at the time of 

 anthesis. 



The spikelet may be considered as a specialised branch 



consisting of a short axis, the 

 rachilla bearing a series of 

 modified bracts, the glumes, the 

 lower pair being empty but the 

 others bearing flowers in their 

 axils. The glumes are two- 

 ranked and imbricating. As a 

 type for the spikelet that of an 

 Eragrostis or Dinebra may be 

 chosen. (See fig. 17.) In this 

 spikelet the rachilla bears a 

 number of glumes alternating 

 and imbricating. The first two 

 glumes at the base of the 

 spikelet do not bear any flowers 

 and so these two glumes are 

 usually called empty glumes. 

 This is the case in almost all the 

 species of grasses. The third 

 and the subsequent glumes are 

 regularly arranged on the slender rachilla alternately in two rows. 

 In the axils of each of these glumes there is a flower, except 

 perhaps in the topmost glume. The flower is usually enclosed by 

 the glume and another structure found opposite the glume and 

 differing very much from the glume. This is the palea. It is 

 attached to the axis of the flower and its back is towards the 

 rachilla. Generally there are two nerves in a palea and its 

 margins are enclosed within those of the glume. The palea is 

 homologous with the prophyllum which it very much resembles. 

 The prophyllum is usually found in the branches of grasses, but it 

 is not confined to grasses alone. It occurs in the branches of some 

 species of Commelina. 



The spikelets vary very much in their structure. The spikelets 

 in grasses of several genera consist of only four glumes. As usual 

 the first two glumes are empty and the remaining two are flower- 

 bearing glumes. Both these glumes may have perfect flowers as 

 in Isachne or the terminal one may contain a perfect flower, the 



FlG. 17. — The Spikelet of Dinebra arabica. 



1 and 2. Empty glumes ; 3, 4, 5 and 6. 

 flowering glumes with flowers. 



