May 11, 1900.] 



SCIENCE, 



749 



mal Forms of Dogwood,' Willard N. Clute has 

 a fifth article on ' The Making of a Herbarium,' 

 and Mrs. Caroline A. Creevey concludes the 

 series devoted to ' Plant Juices and their Com- 

 mercial Values' with a brief paper on dye plants. 

 C. F. Saunders notices ' The Small Mistletoe in 

 Pennsylvania, ' and the editor comments on for- 

 est preservation. Charles Louis Pollard, in the 

 supplement presenting the ' Families of Flower- 

 ing Plants, ' treats of the order Glumifloras — the 

 grasses and sedges. 



SOCIETIES AND ACADEMIES. 



BIOLOGICAL SOCIETY OF VSTASHINGTON. 



The 323d regular meeting was held on Sat- 

 urday, April 5th. C. H. Townsend spoke of 

 ' The Flying Foxes of the South Pacific Islands ' 

 under this title describing the fruit bats, 

 Pteropus, found during the recent voyage of 

 the United States Fish Commission steamer Al- 

 batross, and illustrating his remarks with lan- 

 tern slides and specimens. The speaker stated 

 that no bats were found in Polynesia to the 

 eastward of the Tonga and Samoa groups al- 

 though search was made for them. 



A large rookery of flying foxes on the island 

 of Tongatatu was visited and many fine photo- 

 graphs were taken showing the bats clinging in 

 large numbers to the tree-tops. The rookery 

 is located in a small native settlement near 

 Nukalofa, the bats about 8000 in number, oc- 

 cupying the tops of 14 large trees in the midst 

 of the village. The rookery is carefully pro- 

 tected by the chief of the village, who permitted 

 the naturalist to take away only three specimens. 

 It was understood that they had been guarded 

 by the people from time immemorial, al- 

 though the animals are frugivorous and evi- 

 dences of their depredations on the island fruits 

 were found constantly. 



Mr. Townsend collected many flying foxes 

 at Namuka Island (Tonga group), where they 

 were found scattered in the forest. They were 

 seen in the Fiji and Samoan islands also but no 

 specimens were secured. 



In a paper entitled, 'Acorns as Food,' Mr. 

 V. K. Chesnut, after briefly mentioning the 

 various places where sweet acorns are, or 

 were, used for human food along the Medi- 

 terranean and in the United States and Mexico, 



gave a special illustrated account of the inter- 

 esting manufacturing and chemical processes 

 which have gradually been evolved by the 

 Indians of Mendocino County, California, to 

 extract the tannin and the bitter principle from 

 the bitter acorns. The acorns of the black oak 

 (Quereus calif ornica), chestnut oak (Q.densiflora), 

 and valley white oak (Q. lobata), especially, 

 constitute an important and almost essential 

 portion of the food of these Indians during the 

 greater part of the year. 



Mr. W. A. Orton spoke on the ' Sap-flow of 

 the Maple ' in spring, giving a brief description 

 of the methods of making maple sugar and a 

 report of some of the investigations made at the 

 Vermont Experiment Station under the direc- 

 tion of Professor L. R. Jones. Sap pressure 

 and flow in the sugar-maple occurs at intervals 

 from October to May, when the weather con- 

 ditions are favorable, but is most active for a 

 month during March or April. To produce sap- 

 flow it is necessary that the temperature should 

 rise from several degrees below the freezing- 

 point to some degrees above it. If this change 

 be at all sudden there will be developed a pres- 

 sure within the tree of 15-25 or more lbs. per 

 square inch. Charts showing the relation of the 

 temperatures as measured by a self-recording 

 thermometer, to the sap-pressure recorded by 

 a self-recording steam-pressure gauge attached 

 to a maple tree were exhibited, and it was 

 shown that in general there was a very close 

 relation between sudden rises of temperature 

 and of sap-pressure, there being pressure on 

 warm days followed by suction at night. 

 Sap flow diminished toward the top of the 

 tree. It was greatest in the outer part of the 

 tree, but continued longer from deeper in the 

 wood. It was concluded that the cause of sap- 

 flow was physical rather than physiological, be- 

 ing due to the expansion of confined air and 

 water in the vessels of the wood, brought about 

 by a sudden rise of temperature. There is 

 little if any root-pressure during the season of 

 sap-flow, and as the trees are dormant the old 

 question of ascent of water from roots to leaves 

 hardly enters into the problem. The direction 

 of sap-flow was studied by injecting lithium 

 into the tree near the tap-hole and testing the 

 sap with a spectroscope. It was found that 



