10 



SOUTH INDIAN GRASSES 



portions of these shoots. Three distinct kinds of leaves are 

 met with in grasses. First, we have the fully formed foliage leaves 

 so characteristic of grasses. These are most conspicuous and are 

 formed in large numbers. 



FlG. 12. — I'rophylla. 



A. A branch with its prophylluin ; B 



prophyllum ; C. section of the 



prophyllum. 



The other two kinds of leaves 

 are neither so conspicuous nor 

 so numerous as the foliage 

 leaves. At the base of shoots 

 occur abortive leaves which are 

 really rudimentary sheaths. 

 These are called scales. The 

 third kind of leaf is a modified 

 structure called the prophyll or 

 prophyllum. (See fig. 12.) It is 

 the first leaf occurring in every 

 branch on the side next to the^ 

 main shoot and it is a two-keeled 

 membranous structure resem- 

 bling somewhat the palea found 

 in the spikelets of grasses. The 

 portion of the prophyll between 

 the keels is concave due to the 

 pressure of the main stem, while 

 the sides beyond the keels bend 

 forward clasping the stem. 



The ordinary foliage leaves of grasses consist of the two 



parts, the flat expanded upper 

 portion called the blade and the 

 lower part called the sheath that 

 encircles the stem above the node 

 from which it arises. The leaf- 

 sheaths usually fit close to the 

 stem, but they may also be loose 

 or even inflated. Though the leaf- 

 sheath surrounds the internode 

 like a tube, it is not a closed tube. 

 It is really a flat structure rolled 

 firmly round the stem with one 

 edge overlapping the other. In 

 most cases it is cylindrical and it 

 may be compressed in a few cases. 

 Occasionally it may have a pro- 

 minent ridge or keel down its 

 back. The sheath may be glab- 

 rous or hairy, smooth or striate 

 externally, and the outer margin 

 is often ciliate. In a few grasses 

 the sheaths become coloured 

 2. Panicum javanicum ; 3 Andropogon especially below or on the side 

 Schcenanthus ; 4. a. cuntortus. exposed to the sun. 



FIG, 13. — Ligules of I. Oryza sativa ; 



