416 



THE AMERICAN NATURALIST [\^ol. XL 



Clark found that pressure from the root during the sugar season 

 was never more than very slight. Usually there was suction in the 

 root throughout this period. At the Vermont Station the results 

 were similar, the suction in one case being as much as 2.7 kg. 

 There was a very slight fluctuation, however, between day and 

 night as in nearly all roots. In no case was there a flow of sap 

 from the root until late in April at the time when other trees bleed 

 from the root. The root therefore as a source of bleeding in the 

 maple is out of the question. 



The sap of the maple is composed mainly of water with a few 

 substances in solution. Of these, cane sugar is the most important, 

 being present in from 1 to 5 concentration. At first the sap is 

 a water-clear, slightly sweet fluid, but as the season progresses 

 the flow tends to lessen and the sap is apt to thicken and become 

 cloudy or even somewhat slimy' at times. Besides sugar there are 

 usually small quantities of proteids, of mineral matter, more 

 especially of lime and potash, and of acids mainly malic. Traces 

 of reducing sugars are sometimes found, usually toward the last 

 of the season. The sap from a tap-hole at ordinary height is 

 considerably richer in sugar than the sap from the root, and also 

 richer than that from taps higher up in the tree. The percent of 

 sugar is also greater in sap from near the surface of a tree trunk 

 ' than from deeper in the wood. There is some reason to believe 

 that the actual distribution of stored material during the winter 

 (starch and sugar) follows these conditions closely with less stored 

 starch in the root than above ground, and less in the top than in 

 the trunk, but accurate determinations have not been made. In 

 Vermont it was found that at the beginning of the season sixty 

 percent of the sugar came down from above. At the close of the 

 season only about 39 came from the same source. There 

 seemed to be a slight diurnal fluctuation in the percent of sugar, 

 it being slightly greater toward nightfall. 



varirs fn.in :!()'/ to .V)'/. Aftrr the leave" rnuw out it falls to 

 from 111 to ;!()/. Tlu- \Crinoiif workiT.s foinid the rrlativc amount 

 for root, trunk, branch, and twig to be 2<), .'iO, :>4, and 37 respec- 

 tively, but variations were so wide that the value of the series of 

 averages is open to ciuestion. 



