HOLE : SOME INDIAN GRASSES AND THEIR CECOLOGY. 57 



to determine its size and state of development in any previous month (provided that growl h 

 had been continuous) and this would greatly facilitate the inquiry. 



The culms of most grasses are annual and if such an annual culm is examined it will, 

 as a rule, exhibit two or more very short internodes at the extreme base which can be clearly 

 distinguished from the subsequent much longer internodes. In other words such a culm 

 exhibits more or less distinctly two periods of growth — 



(a) a preparatory period of slow growth; 



(b) a subsequent period of vigorous growth. 



The short internodes produced during the preparatory period carry only scales, or else 

 small and obviously under-sized leaves. The internodes produced during the period of 

 vigorous growth, on the other hand, carry well-developed green leaves. These internodes 

 are also, as a rule, much longer than those of the preparatory period, but in some cases 

 (especially in species like Saccharum Munja, the culms of which are biennial) several of 

 them remain as short as those of the preparatory stage. A culm in the preparatory stage 

 of growth is obviously merely a bud which possesses as yet no well-developed leaves and 

 for practical purposes the life-cycle of a culm may be considered to commence with the 

 period of vigorous growth, i.e., with the first production of well-developed leaves which is 

 often (but not always) correlated also with the first production of long internodes and the 

 commencement of a marked increase in length. 



As regards the development of the culm during the period of vigorous growth, observ- 

 ations made at Dehra Dun on the sand-form of Saccharum spontaneum showed that in this 



plant, in this locality : — ■ 



(1) The period of development of an internode carrying a well-developed leaf at its 



apex approximately commences with the first appearance of the leaf at its 

 apex and terminates with the complete withering of* that leaf (including the 

 sheath). This period can therefore be determined by noting respectively the 

 date of appearance and of the withering of the leaf at its apex. In this 

 species the period observed was five months. In one month therefore ' one 

 internode with the leaf at its apex completes g-th of its life-cycle. 



(2) The total number of internodes of the culm carrying well-developed leaves and 



which are in active growth at one and the same time is 5 and therefore the 

 growth of the whole culm during the period of vigorous activity proceeds at 

 the rate of one complete internode per month. 



(3) The period between the commencement of the growth of one internode and of 



the internode which immediately succeeds it is one month. 



If we assume therefore that all the internodes carrying well-developed leaves require 

 the same period for their development and if we consider the life-cycle of the culm to 

 commence from the time when the terminal tuft of 5 green leaves each carrying an obvious 

 screen lamina has become visible, it is clear that at the end of the first month the first leafv 



[ 57 ] 



