HOLE : SOME INDIAN GRASSES AND THEIR (ECOLOGY. 95 



B. — Taxonomy. 



74. According to published descriptions, 

 Imperata exaltata, Brongn, the area of distribution of which, to some extent, overlaps 

 that of the present species, is distinguished from the latter mainly by the following 

 characteristics : — 



(1) Panicle thyrsiform, 4 — 5 inches broad at base (F. B. I., VII, 107). 



(2) Stamen one. 



(3) Upper spikelets in racemes solitary. 



(4) Culm fistular. 



(5) Glumes I and II three nerved with mid-nerve reaching, or almost reaching, the 



apex of glume. 

 It is therefore interesting to note that, in the local specimens of Imperata arundinacea, 

 Cyrill, the culms are slightly fistular at the base, glumes I and II have 3 — 6 nerves and the 

 upper spikelets in the racemes are sometimes solitary. 



75. Of Imperata arundinacea three forms can 

 be more or less clearly distinguished locally as under : — 



(a) The depauperate form common on lawns or areas where the grass is continually 



cut or grazed, with minute, almost filiform, culms and small leaves. Leaf- 

 insertions usually long-bearded. Glume IV and pale usually glabrous. 



(b) The ordinary savannah form which usually attains a height of about 3 ft. with 



leaves up to 0-7 in. wide. Leaf-insertions bearded, or glabrous. Pale and 

 glume IV ciliate. 



(c) A robust form found in swamps or marshy soil where there is an abundance of 



available moisture more or less throughout the year. This plant attains a 

 height of 9^ ft. and probably more. Leaves up to 1-1 in. wide, leaf -insertions 

 glabrous. Pale and glume IV ciliate. (This plant is var. lati folia Hook f .) 



The mode of occurrence of these different forms in their natural habitats and the fact 

 that numerous intermediates are met with, as the conditions vary, indicate that such 

 characters as the vigour of growth (indicated by the diameter and height of the culms, 

 length of the panicles, length and width of the leaves), the hairiness of the nodes, of glume 

 IV and of the pale, are directly dependent on the nutrition of the plant and it is believed 

 that form {a) owes its characteristics to the starving effect of the artificial interference 

 with its normal growth and development, while the peculiarities of form (c) are due to the 

 exceptionally favourable conditions of available moisture under which it grows. 



Plants of all these forms are now being cultivated at Dehra Dun with the object of 

 testing the effect of protection on (a) and of a diminished water supply on (c). 



Hackel has subdivided Imperata arundinacea into three varieties of which he further 

 distinguishes sub-varieties, depending mainly on such characters as the hairiness of the leaf- 

 insertions, width of the leaves and height of the ligule. The height and shape of the ligule, 

 however, is more or less correlated with the width of the lamina, while the other characters 

 appear to vary with the locality as indicated above and do not define forms of any constancy. 



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