5(3 INDIAN FOREST MEMOIRS. 



The xerophilous form of the species, on the other hand, which shows much inferior 

 height growth, very slender, stiff and almost wire-like culms and very narrow leaves, as a. 

 rule resists the laying action of water well. At the same time isolated culms of this form 

 have been seen laid by water and rooting to a distance of 2 — 4 feet from the parent plant. 



The above remarks on habit may be summarised as follows : — ■ 



(1) The species shows a markedly xerophilous form frequent on dry sand, a hygro- 



philous form where an abundance of water is available and a form inter- 

 mediate between these two which is common on agricultural lands, wet 

 pastures, etc. 



(2) The xerophilous form which often occurs on the dry sand deposits brought down 



by torrents in the rains, is liable to be covered by accumulations of water-borne 

 (and possibly to some extent wind-carried) sand and debris, and it usually 

 shows a marked tufted habit which is advantageous in enabling the plant to 

 avoid being smothered. The stiff slender culms and small very narrow leaves 

 of this form enable it to resist the mechanical action of wind and water and 

 it is rarely " laid " in consequence. See Plate XIV. 



(3) The intermediate form, common on agricultural lands and usually on loam, with 



a more or less constant surface level, shows a spreading habit which enables 

 the plant to rapidly extend and occupy large areas. See Plate XIII. 



(4) The hygrophilous form also shows a spreading habit and this is to some extent 



at least caused by its liability to be " laid " by water currents and possibly 

 also to some extent by wind. See Plates III and XV. 



Immature leafy culms of this species were cut over in the Dehra Dun garden and the 

 effect of the cutting on their growth carefully watched. The cutting was done in such a 

 way as not to injure the apical bud of thte culm itself but to more or less destroy the green 

 leaves existing on the culm when the cutting was done. The first thing noticed was that 

 the destruction otf the green leaves resulted in greatly diminishing the length of the inter- 

 nodes of the culm. See Plate XVIII, figs. 7 and 8. A series of abnormally short inter- 

 nodes preceded and succeeded by normal long internodes are frequently seen in the culms 

 of this and other species and these, as a rule, indicate that the leaves of such culms have 

 been more or less destroyed by the grazing of cattle, grass-cutting, or fire. 



In order to study the susceptibility of any grass to fire-damage at any particular season 

 it is obviously necessary to be acquainted with the life-history of the culms and to know 

 what their usual state of development would be at that season. The development of the 

 culms cannot be always satisfactorily studied in the Experimental Garden, as it often tends 

 to there become more or less abnormal. Direct observation in the forest throughout the 

 year is often not practicable and is in any case tedious. If, therefore, a method could be 

 discovered by which the age of a culm could be approximately calculated at sight, and if 

 its rate of development were known, it is obvious that a single observation would enable us 



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