August i i, 1923] 



NATURE 



207 



191 2 [by Capt. C. S. Wright] at Cape Evans was 

 983-003 from the July series and 983-004 from the 

 August series. . . . Commander Bernacchi . . . ob- 

 tained the values 982-970, 982-979, and 983-025. . . . 

 These values may be compared with the standard 

 value 981-292 at Potsdam. . . ." 



This suggests the existence of a substantial 

 difference between the results of the two British 

 expeditions. This does not, however, seem to be 

 the case. The final value for g derived from Com- 

 mander Bernacchi's observations (National Antarctic 

 Expedition 1 901-1904, " Physical Observations," 

 Table V., p. 34) was 982-985. In obtaining this, for 

 reasons stated in the discussion, half weight only 

 was allowed to the third pendulum. Thus the 

 apparent difference between the results from the two 

 expeditions is 0-0185 cm. /sec. 2. But this is accounted 

 for by the fact that while Capt. Wright accepted 

 for g at Potsdam — on which all the Antarctic results 

 really depend — the value 981-292 quoted by your 

 reviewer, I accepted 981-274 on the authority of 

 Sir Gerald Lenox-Conyngham (Roy. Soc. Proc. A, 

 vol. 78, p. 245). The-difference between these two 

 assumed values is o-oi8 cm. /sec. 2. Thus the values 

 obtained by the two Antarctic expeditions — not 

 exactly at the same place — really agreed to six 

 significant figures. Though not assigning the im- 

 portance that Paley did to " undesigned coincidences," 

 I think this coincidence is remarkable enough to be 

 worth mentioning. It would be of interest in this 

 connexion to know what value the German experts 

 assign now to g at Potsdam. C. Chree. 



June 30. 



i 



The Translocation of Carbohydrates in the 

 Sugar Maple. 



The conclusion of Prof. H. H. Dixon (Nature, 

 •"ebruary 23, 1922, p. 236, and October 21, 1922, 

 547) that the translocation of organic substances 

 pould take place through the vessels of the xylem 

 lippears to have created a mild sensation among 

 slant physiologists. Attention, however, does not 

 Seem to have been directed to the behaviour of the 

 Sugar maple, which furnishes important evidence in 

 this connexion. 



The sugar maple or rock maple {Acer saccharum, 

 larsh) is well known in Eastern Canada and New 

 England as the source of the maple syrup and maple 

 sugar of commerce. To obtain the sap, a small 

 "lole about half an inch in diameter is bored into 

 ^he sapwood to a depth of about 3 inches, at a height 

 )f about 4 feet above the ground-level at the time 

 irhen the snow is melting at the beginning of spring, 

 metal tube is inserted into the hole, and a small 

 )ucket is attached into which the sap drops from 

 the metal spout. The sap as it oozes from the tree 

 colourless, but becomes brown on concentration 

 )y boiling. 



A bulletin entitled " The Maple Sap Flow," by 



[ones, Edson, and Morse, published by the Vermont 



agricultural Experiment Station in 1903, gives a full 



iccount of observations and experiments on this 



lubject. Some of the conclusions reached by these 



ivestigators are as follows : The sap contains about 



per cent, of sucrose and also small amounts of 



i)rotcids, mineral matter, and acids, mainly malic 



icid. The greatest sap flow does not occur at the 



time when the most water is contained in the tree. 



lore sap flowed at the opening of the sugar season 



than at the close when more water was in the tissues. 



There is no evidence that the water is forced into the 



maple trunk by root pressure at any season. 



NO. 2806, VOL. I 12] 



Warm sunny days and freezing nights form ideal 

 sugar weather. On good sap days the pressure from 

 above downwards is greater than that from below up- 

 wards. The flow generally, but not always, parallels 

 the pressure. Later in the season and upon poor sap 

 days, upward pressure and flow exceed those from 

 above. The fastest run of sap from a tap hole 

 during the experiments was 17-7 c.c. per minute. 

 Jones and Orton, using lithium chloride, had previously 

 determined the rate of flow in either direction as 

 2 to 6 inches per minute. 



Some observations on this subject were made 

 during the spring on two trees, numbered respectively 

 185 and 3389, growing in the Botanical Garden at 

 Ottawa. In order to determine whether the flow 

 of sap came from the bark or the wood, several small 

 branches on each tree were chosen which projected 

 horizontally or inclined slightly upward. These were 

 cut across at right angles to their length on March i, 

 1923, the cut end was smoothed and the bark peeled 

 off close to the wood for a distance of about an inch 

 from the cut end. In tree No. 185 sap commenced 

 to flow on April 11 and ceased on April 27, while in 

 tree No. 3389 the respective dates were April 17 and 

 May 14. In no instance was sap observed to exude 

 from the cut surface of the bark. Several observa- 

 tions were made on the rate of flow of sap from a cut 

 branch together with records of temperature, etc. 

 In tree No. 185 a branch measuring 15 mm. in 

 diameter (including the bark) was selected, while in 

 tree No. 3389 the diameter of the branch was 18 mm. 

 The number of drops falling per minute was counted ; 

 the diameter of each drop was about 5 mm. Some 

 of the results were as follows : 



April 19, 1923. Tree No. 185. Time, 3.40 p.m. 

 Shade temperature =50° F. Fifty-one drops fell in 

 five minutes. 



April 20, 1923. Tree No. 185. Time, 3.15 p.m. 

 Shade temperature = 77° F. Sunny. Two counts 

 gave 8 drops each per minute. 



April 16, 1923. Tree No. 3389. Time, 3 p.m. 

 Shade temperature = 38° F. Snow was still lying 

 round the base of the tree. Sap was flowing at the 

 rate of 18 drops in five minutes. Another count 

 gave 17 drops in five minutes. 



April 19, 1923. Tree No. 3389. Time, 3.55 p.m. 

 Shade temperature = 50° F. Some snow still around 

 the base of the tree. Drops were falling at the rate 

 of 115 in five minutes. Another count gave 22 drops 

 in one minute. 



A microscopical examination of twigs cut from 

 each tree on March i and on May 7, on which date 

 the buds were swelling, showed abundant starch 

 grains in the medullary rays but none in the pith 

 on both occasions. The amount of water present 

 in several small branches half an inch in diameter 

 taken from each tree was also determined for the 

 above dates, when it was found that each tree con- 

 tained i per cent, less water on May 7 than it did 

 on March i. 



The spring flow of sap was also observed in five 

 other species of maple growing in the Botanical 

 Garden here. In Acer Myabei on April 14 an icicle 

 measuring 9 inches long and i^ inches wide at the 

 base was observed hanging from a broken branch. 



While some points in the metabolism of the maple 

 sap may still be obscure, it is abundantly evident 

 that the vessels of the wood are able to carry the 

 sugar solution in both directions in the tree -trunk 

 and that the rate of flow is comparatively rapid. 



J. Adams. 



Central Experimental Farm, Ottawa, 

 July II. 



