HOLE : SOME INDIAN GRASSES AND THEIR CECOLOGY. 



I.:; 



Of the greatest importance for vegetation also are the maximum temperatures recorded in 

 the sun's rays and the minimum temperatures on the grass, regarding which no reliable 

 figures are available for years subsequent to 1890. 



The following figures show the maximum temperature recorded in the sun each month 

 during the three years 1888 — 90 : — 



Maximum reading in sun's rays by Black Bulb Thermometer. 



Tear. ' January. 



I 



February. 



March . 



April. 



May. 



June. 



July. 



August. 



September. | 



October. 



November. 



December. 



1SS8 

 1889 

 1890 



126°-7 



131 -5 



132 -8 



132°-5 

 133 -5 



136 -4 



146° -9 

 144-4 

 143-5 



153°-5 

 155-3 



157-8 



155°-5 

 159-0 

 157-5 



161'-0 

 157-3 

 155-3 



156°-0 

 158-7 

 159-6 



155°-4 



157-0 

 152 -S 



151°-5 



154-0 

 151-2 



142°1 

 142-9 

 143-6 



135°-9 

 136 

 132 -6 



126°-0 

 129 -1 

 130-6 



Mean 



130 3 



134 -1 



144-9 



155-5 



137-3 



157 9 158-1 



155-1 



152 "2 



142 -9 134 -8 



128-6 



The highest temperature recorded being 161° registered in June 1888. These figures 

 indicate the temperature which may be reached in grasslands surrounded by forest where 

 there is little or no circulation of air. 



The following figures show the minimum temperatures recorded on the grass for the 

 same period, as recorded at Dehra Meteorological Station : — 



Minimum reading on grass taken at 9-30 a.m. 



Tear. 



January. 



February . 



March. 



April. 



May. 



June. 



July. 



August. 



September. 



October. 



November. 



December. 



1888 



1 



31°'2 



36°-2 



47°-2 : 



46°-l 



55°-2 



63°-0 



68°-6 



67°0 



61°-3 



47°-3 



39°-7 



35°4 



1889 



35-0 



30-3 



43-8 



49-3 



58-0 



66-9 



68-1 



68-8 



56-4 



47-2 



38-9 



32-4 



1890 



32 -1 



34-7 

 33-7 



43-8 

 44-8 



50-2 



59-8 



65-4 



69-7 



66 5 



59-4 



47-9 



40-3 



37-1 



Mean 



32 -8 



48*5 



57-7 



65 1 



68-8 



67-4 



59 



47-5 



39-6 



35-0 



In many of the forest grasslands of the locality, however, considerably lower tempera- 

 tures are undoubtedly reached than those recorded at Dehra Dun Station. Frost is 

 frequently observed in these grasslands during December and January and is in many cases 

 the principal factor responsible for the absence of tree growth. 



The period of maximum vegetative activity for most of the grasses dealt with in this 

 paper is, as might have been expected, the rainy season from June to September. 1 



It is remarkable, however, that almost all these species show a certain degree of activity 

 throughout the year, with the exception of the months December — January. In these 



In the ease of one st ecies, Imperata arundinacea, it is remarkable that maximum growth usaalty takes place in the pe'-iod March — May. 



[ 43 ] 



