HOLE : SOME INDIAN GRASSES AND THEIR ECOLOGY. o5 



47. This plant is perennial and usually J f c ™i° ] JJ Mm,i 



gregarious. The culms originate from the basal nodes of older culms either above or below season of 



& o o t Vegetative 



the ground surface. A culm which originates below the ground surface may either at once Activity ami 

 assume an erect habit of growth, in which case the young culms arise in the immediate 

 neighbourhood of the older culms and a more or less clearly defined tuft or clump results, or 

 else the young culm may grow for some time in a horizontal or oblique direction below the 

 ground surface, before its apex eventually turns upwards and assumes an erect habit of 

 growth. In the latter case the culms are widely scattered and no tuft or clump is found. 

 In this respect this species differs from the other species of Saccharum and Erianthus dealt 

 with in this paper in which each culm at first only grows outwards in a more or less hori- 

 zontal direction at the base for a very short and constant distance before eventually turning 

 upwards and becoming erect and in which a new bud at once arises and continues this 

 horizontal growth, as the older culm becomes erect. In these species therefore the growth 

 resembles that of a typical rhizome, whereas in S. spontaneum there is no well-defined 

 rhizome. 



In the other species of Saccharum and Erianthus dealt with, also, the culms usually 

 arise close together and form well-marked clumps. In S. Narejiga, however, a tendency 

 towards a spreading habit and the consequent production of ill-defined clumps is some- 

 times seen. 



The present species in this locality is often found on sand in and near the beds of 

 water-courses and in such places the plant is liable to be covered by masses of sand and 

 debris brought down by floods. It is only under these conditions that the tufted habit 

 prevails and this appears to be an obvious adaptation which facilitates the rapid produc- 

 tion of aerial culms from the ground surface and prevents the plant being overwhelmed and 

 smothered by accumulations of debris and sand. In relatively stable soil, such as the loamy 

 soil of cultivated areas, the spreading habit prevails and enables the plant to extend and 

 occupy large areas far more rapidly than would be possible with the tufted habit of 

 growth. 



In places where the plant is directly exposed to the rush of a water current, the spread- 

 ing habit is also common and this is to a great extent caused by the young culms beino- 

 " laid " by the mechanical action of the water, just as are often cereals by heavy wind. 

 Culms which are thus laid prostrate are often covered more or less deeply with sand and 

 root at the nodes and they then look exactly like the ordinary subterranean rhizome 

 branches. The more luxuriant the growth, the taller and larger the culms and the larger 

 the leaves, the more liable is the plant to be laid in this way. 



The luxuriant form of the species (which has been named nepalense by some botanists), 

 therefore, which is often found in or close to the beds of streams is particularly liable to 

 this action and considerable areas have been seen where all the culms of this plant have been 

 laid perfectly flat and more or less covered with sand. There is little doubt therefore that 

 the spreading habit exhibited by this form is to a great extent caused in this way. 



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