68o THE AMERICAN NATURALIST. [Vol. XXXVIII. 



has long wished to have. The paper is of such length (184 pages, 

 8vo) that even an abstract may easily be too long for this journal. 



After an introduction, stating the importance of the maple-sugar 

 industry, the process of sugar-making, and former investigations, the 

 authors proceed to describe their plan of work and the scope of their 

 investigations. A few pages are given to the structure and general 

 physiology of the maple. In sixty pages the authors discuss (i) the 

 water and gas contents of the maple at di^^erent seasons, comparing 

 it with other trees ; (2) pressure, positive and negative, at different 

 seasons, in different parts of the tree, and the direction of pressure 

 and sap movement ; (3) temperatures, comparing internal with exter- 

 nal. It is to be hoped that this study of external temperatures will 

 be supplemented by further ones. The authors studied only air 

 temperatures, but it is obvious that the temperatures of the soil must 

 have at least an equal, if not a greater, bearing on the phenomena 

 of sap flow in the spring than the air temperatures. As others have 

 shown, the roots begin to be active much earlier than the aerial parts 

 of trees and shrubs growing in the temperate zone. This early re- 

 sumption of active life in the roots, and the energetic absorption of 

 water from the soil, depend more directly on soil temperatures 

 than on air temperatures. Hence, if we are thoroughly to under- 

 stand the process of periodic sap flow, we must know all the condi- 

 tions, not merely those in the air and in the aerial parts of a tree. 

 It may not be too much to suggest also that studies of the water- 

 content of soil and air before, during, and after sugaring time would 

 be a valuable addition. This is intimated by the authors, though the 

 subject is not pursued further. 



The remaining seventy pages are occupied by a discussion of eco- 

 nomic problems and by tabular reports of weather conditions, etc. 



The Journals.— 77/^ Botanical May Sargant, " The 



Evolution of Monocotyledons"; Smith, "The Nutrition of the Egg 

 in Zamia"; Opperman, ''A Contribution to the Life History of 

 Aster"; Cardot and Theriot, ''New or Unrecorded Mosses of North 

 America"; Livingston, " Physical Properties of Bog Water ^ Rose, 

 "William M. Canby"; Ramaley, " Anatomy of Cotyledons." 



TheBryo!osist,^l^y..-i^,o^xl, "The Peristome -VI Holzinger, 

 Rhacomitrium Flettti, n. s^.- ■ Holzinger, "A Bryologist's Glimpse 

 into Geological History"; Harris, " Lichens — CoUema and Lepto- 



