202 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XX. 



water be veiy slow. The water helps to feed the plant with mineral solutions 

 •on its way to the leaves from whose surface it escapes by evaporation at a 

 varying rate, according to the season or time of day. Botanists seem to agree 

 in saying that plants have no organs for absorbing water or vapour through 

 the leaves. The movement of water must therefore be always in one direc- 

 tion which would seem to imply the existence of some kind of valve on the 

 surface of the leaves, which prevents a reverse movement, even when under the 

 influence of atmospheric changes of temperature and pressure. In Bombay we 

 learn from figures kindly furnished by Mr. N. A. Moos at the Observatory, that 

 the mean monthly solar radiation as recorded by the black bulb thermometer 

 in the month of January, is 133*5 degrees Fahrenheit and that the minimum 

 grass radiation thermometer at night indicated 62*5 degrees, shewing a range 

 of 71 degrees to which plants are exposed. These are only mean figures. In 

 Allahabad the sun temperature rises to 163 degrees, giving in all probability 

 a much greater range. Confined air under an increase of temperature equal 

 to 71 degrees would increase in pressure by about 2'8 lbs. per square inch or 

 approximately 403 lbs. per square foot. The range of barometric pressure 

 an Bombay is small as compared with that of other countries. It occurs in 

 two daily waves having their maxima at ten o'clock, morning and evening, and 

 their minima at four o'clock, morning and evening. The maximum range 

 is equal to a column of water 7-936 inches high, which corresponds with a 

 pressure per square foot of 41*98 pounds. The atmospheric influence acting 

 on the Ukshi are thus a wave of temperature, rising from sunrise until half 

 past two o'clock in the afternoon and falling until sunrise ; and two waves of 

 barometric pressure of an amplitude already indicated. It is hard to believe 

 that such forces, acting on the outside of a plant, whose juices have to be 

 raised against gravity and friction, should have no useful influence in assisting 

 its functions. This assistance would seem to involve the existence of valves, 

 and as this matter has been the subject of contrary opinions there is still a lack 

 of unanimity about it. .Col. Kirtikar recently examined a vertical section of a 

 local fresh plant, and observed that it has innumerable pitted cells which Prof. 

 Strasburger of Bonn University in 1903 found to act apparently as valves. 



We all know that it is not the heart alone that circulates the blood in an 

 animal body, because the whole work, if thrown on that organ alone, would 

 rupture it. We may with safety assume that the water column circulating 

 through the comparatively wide vessels of the Calycopteris floribunda are not 

 continuous, and it remains for us to ascertain exactly the form of interruption 

 which supports the water column, and the extent to which the meteorological 

 changes, above referred to, affect the circulation of the plant whose extremi- 

 ties are open to absorption of water at the lower ends and to evaporation of 

 moisture at the upper ends, while both extremities, owing to their conforma- 

 tion, do not permit a reverse current. It seems as if the regularly recurrent 

 changes of temperature and pressure represent forces sufficient to carry on 

 the work of circulation if the organs of the plant are adapted to utilise them. 



