SOME EXPERIMENTS ON THE SAP OF PLANTS. 261 
And that birch-sap contains sugar is known, the peasants of many 
countries, especially Russia, being well acquainted with the art of 
making birch wine by fermenting its saccharine juice. 
But after searching two or three large libraries of scientific 
societies I could not find any hourly or daily record of the amount 
of sugar-bearing sap which can be drawn from the birch, or that 
of any sap from any tree, before the tree has acquired its great 
digesting or rather developing and transpiring apparatus—its leaf- 
system ; nor could I meet with any extended chemical analysis of 
sap, either of the birch or other tree. 
But to proceed with a description of the experiments. <A bottle 
was so suspended beneath the wound as to catch the whole of the 
exuding sap. It caught nearly 5 fluid ounces between eight and 
nine o’clock p.m. During the succeeding eleven hours of the night 
44 fluid ounces were collected, an average of 4 ounces per hour. 
From 8.15 to 9.15 on the morning of the 4th, very nearly 7 ounces 
were obtained. From 9.15 to 10.15, with bright sunshine, 8 ounces. 
From 10.15 until 8.15 in the evening the hourly record kept by 
my son Harvey showed that the amount during that time had 
slowly diminished from 8 to a little below 7 ounces per hour. Ap- 
parently the flow was faster in sunshine than in shade, and by day 
than by night. The flow was observed from time to time for nearly 
a week, the rate mentioned being maintained. The wound was 
open altogether for 21 days, hence probably rather more than 17 
gallons of sap exuded during 20 days of that time; for my 
excellent gardener, Jonathan White, assured me that the tree had 
been “ bleeding” at about the same rate for fourteen of the fifteen 
days that elapsed before the matter came under my notice, the first 
day the branch becoming only somewhat damp. 
It would seem, therefore, that this slender tree, with a stem 
which at the ground is only 7 inches in diameter, having a height 
of 39 feet, and before it has any expanded leaves from whose 
united surfaces large amounts of water might evaporate, is able to 
draw from the ground about 4 litres or seven-eighths of a gallon of 
fluid every twenty-four hours. That at all events was the amount 
flowing from this open tap in its water-system. Even the topmost 
branches of the tree did not become during the three weeks abnor- 
mally flaccid, so that presumably no drainage from the upper portion 
of the tree had been taking place. Besides, after due calculations, 
I find that the amount of fluid which would exude in the three 
weeks would be greater than could be contained in the whole of 
the trunk and branches above the wound even if they were hollow. 
For three weeks, therefore, the tree had been drawing, pumping, 
sucking—I know not what word to use—nearly a gallon of food 
daily from the soil in the neighbourhood of its roots. This soil 
had only an ordinary degree of dampness. It was not wet, still 
