^be Stor^ ot tbe Stem 37 



color in bark and bud which suggests the circulation 

 of the sap ; something of that difference which 

 appears between a dead and a sleeping human body. 

 In fact, in February the sap has already begun to 

 rise, as is testified in many parts of the country by 

 the active work in the sugar maple groves, where 

 gallons of sap are being collected and boiled. From 

 almost any stem, if now cut across, water will drip. 

 This water, or sap, the life-blood of the plant, is 

 forced up by root pressure, which is especially great 

 in the early months of the year. One botanist found 

 that in a portion of grapevine this pressure of sap 

 up from the root had a force sufficient to support a 

 column of mercury over thirty-two inches high. In 

 some plants, especially young and tender specimens, 

 the root drives up the sap at such a furious rate that 

 it presses it through the epidermis, and causes it to 

 stand in drops on the surface. A very simple 

 experiment proves that this upward rush of sap is 

 caused by pressure from the root ; take any stem 

 from which drops are issuing, cut it from the main 

 stock or root, and place it in water — no more dro^^s 

 will appear. Of course, these drops are not pure 

 water, but hold various substances in solution, and 

 these mineral particles will be built up into plant 

 stuff. 



As we examine stems in February or March and 



